X-RAY OF IVU
Indications
1. Check for normal function
of kidneys.
2. check for anatomical
variants or congenital anomalies (e.g. horse-shoe kidney)
3. Check the course of the
ureters.
4.Detect and localize a ureteric
obstruction (urolithiasis)
5. Assess for synchronous
upper tract disease in those with bladder transitional cell carcinoma (TCC)
Patient Preparation:
১। সাধারণত
কোন
রোগীর
কিডনী
ইউরেটার
ব্লাডারে
পাথর
বা
অন্য
কোন
সমস্যা থাকলে IVU
এক্স-রে
Advice করা
হয় ।
২। IVU এক্স-রে করার ৩ দিন আগে থেকে রোগীর খাদ্য তালিকা নিম্নরুপঃ
রোগী লাউ,পেঁপে, কলা, সবজী, ডাল, ডিম ও বড় মাছ মিশ্রিতি তরকারি খাবে। কোন অবস্থাতে ছোট মাছ ও মাংস মিশ্রিত তরকারি খাওয়া যাবে না।
৩। উক্ত ৩ দিনে Tablet, Duralax ২+০+২ X ৩ দিন। Castrol Oil – 30 ml ৩য় দিন রাতে শোবার সময় খাবে।
৪। Serum Creatinine Report নিয়ে
আসতে হবে।
৫। ৪র্থ দিন সকাল বেলা নির্ধারিত সময়ে খালি পেটে প্রয়োজনীয় সকল পরিক্ষার রিপোর্ট নিয়ে IVU এক্স-রে
করার জন্য আসতে হবে।
Procedure:
১। নির্ধারিত দিনে রোগী এক্স-রে করতে আসলে প্রথমে জানতে হবে Serum creatinine
report normal আছে কিনা।
২। রোগী খালি পেটে আছে কিনা এবং পাতলা পায়খানা ও বমি হয়েছে কিনা জানতে হবে ।
৩। সকালবেলা রোগীর পায়খানা হয়েছে কিনা জানতে হবে।
৪। উপরের সব ঠিক থাকলে Plane X-ray KUB নিতে হবে, তাতে বুঝা যাবে রোগীর IVU এক্সরে করার Preparation ঠিক আছে কিনা, যদি না থাকে soap water enema দিয়ে পেট পরিষ্কার করতে হবে এবং মূল X-ray শুরু করতে হবে।
৫। মূল X-ray শুরু করার আগে জানতে হবে রোগীর এলার্জি অথবা হাঁপানি রোগ আছে কিনা। এর কোনটা থাকলে ডাক্তারের পরামর্শক্রমে Inj, Phenergan/ Inj,
Oradexon/ Inj, Cotson যেটা advice করেন, সেটা লাগাতে হবে।
৬। রোগীকে সোজা করে Supine Position- এ শোয়াতে হবে।
৭। X-ray টেবিলে Pressure Band লাগাতে হবে।
৮। রোগীর শরীরে I.V Cannula লাগাতে হবে।
৯। Pulse, Blood Pressure
এবং Temperature ঠিক আছে কিনা দেখতে
হবে।
১০। এইবার রোগীকে I.V Contrast
Omnipaque অথবা অন্য কোন Brand লাগাতে হবে, প্রতি কেজি Body weight- এর জন্য 1 ml.
১১। Contrast দেওয়ার সময় খেয়াল রাখতে হবে ঘড়ির সময়।
১২। প্রথমে ১ মিনিট ফিল্ম নিতে হবে।
১৩। ২য়, ৩ মিনিট ফিল্ম নিতে হবে।
১৪। ৩য়, ৫ মিনিট ফিল্ম নিতে হবে এবং ৫ মিনিট নেওয়ার পর Pressure Band বেঁধে দিতে হবে।
১৫। ৪র্থ, ১৫ মিনিট ফিল্ম নিতে হবে ২ কিডনী দেখার জন্য
১৬। ৫ম, Reduce অথবা ২৫ মিনিট Full length নিতে হবে Pressure Band খোলার পর। এ সময়ের মধ্যে কিডনী ভালো না আসলে delayed ফিল্ম নিতে হবে।আর ইউরেটার ভালো না আসলে Prone Position এবং Oblique Position Film ফিল্ম নিতে হবে।
১৭। প্রস্রাবের চাপ হলে পূনরায় Full Bladder এক্স-রে নিতে হবে। এক্স-রে ঠিক থাকলে, রোগীকে Wash Room এ পাঠাতে হবে এবং বলতে হবে ভালভাবে প্রস্রাব করে আসার জন্য।
১৮। সব শেষে Empty Bladder Film নিতে হবে।
Anatomy kidneys
The kidneys are bilateral bean-shaped organs, reddish-brown in colour and located in the posterior abdomen. Their main function is to filter and excrete waste products from the blood. They are also responsible for water and electrolyte balance in the body.
Metabolic waste and excess electrolytes are excreted by the kidneys to form urine. Urine is transported from the kidneys to the bladder by the ureters. It leaves the body via the urethra, which opens out into the perineum in the female and passes through the penis in the male.
In this article we shall look at the anatomy of the kidneys – their anatomical position, internal structure and vasculature.
Fig 1 – Overview of the urinary tract.
Anatomical Position
The kidneys lie retroperitoneally (behind the peritoneum) in the abdomen, either side of the vertebral column.
They typically extend from T12 to L3, although the right kidney is often situated slightly lower due to the presence of the liver. Each kidney is approximately three vertebrae in length.
The adrenal glands sit immediately superior to the kidneys within a separate envelope of the renal fascia.
Kidney Structure
The kidneys are encased in complex layers of fascia and fat. They are arranged as follows (deep to superficial):
Renal capsule – tough fibrous capsule.
Perirenal fat – collection of extraperitoneal fat.
Renal fascia (also known as Gerota’s fascia or perirenal fascia) – encloses the kidneys and the suprarenal glands.
Pararenal fat – mainly located on the posterolateral aspect of the kidney.
Fig 2 – The external coverings of the kidney.
Internally, the kidneys have an intricate and unique structure. The renal parenchyma can be divided into two main areas – the outer cortex and inner medulla. The cortex extends into the medulla, dividing it into triangular shapes – these are known as renal pyramids.
The apex of a renal pyramid is called a renal papilla. Each renal papilla is associated with a structure known as the minor calyx, which collects urine from the pyramids. Several minor calices merge to form a major calyx. Urine passes through the major calices into the renal pelvis, a flattened and funnel-shaped structure. From the renal pelvis, urine drains into the ureter, which transports it to the bladder for storage.
The medial margin of each kidney is marked by a deep fissure, known as the renal hilum. This acts as a gateway to the kidney – normally the renal vessels and ureter enter/exit the kidney via this structure.
Fig 3 – The internal structure of the kidney.
Anatomical Relations
The kidneys sit in close proximity to many other abdominal structures which are important to be aware of clinically:
Anterior
Posterior
Left
Suprarenal gland
Spleen
Stomach
Pancreas
Left colic flexure
Jejunum
Diaphragm
11th and 12th ribs
Psoas major, quadratus lumborum and transversus abdominis
Subcostal, iliohypogastric and ilioinguinal nerves
Right
Suprarenal gland
Liver
Duodenum
Right colic flexure
Diaphragm
12th rib
Psoas major, quadratus lumborum and transversus abdominis
Subcostal, iliohypogastric and ilioinguinal nerves
Arterial Supply
The kidneys are supplied with blood via the renal arteries, which arise directly from the abdominal aorta, immediately distal to the origin of the superior mesenteric artery. Due to the anatomical position of the abdominal aorta (slightly to the left of the midline), the right renal artery is longer, and crosses the vena cava posteriorly.
The renal artery enters the kidney via the renal hilum. At the hilum level, the renal artery forms an anterior and a posterior division, which carry 75% and 25% of the blood supply to the kidney, respectively. Five segmental arteries originate from these two divisions.
The avascular plane of the kidney (line of Brodel) is an imaginary line along the lateral and slightly posterior border of the kidney, which delineates the segments of the kidney supplied by the anterior and posterior divisions. It is an important access route for both open and endoscopic surgical access of the kidney, as it minimises the risk of damage to major arterial branches.
Note: The renal artery branches are anatomical end arteries – there is no communication between vessels. This is of crucial importance; as trauma or obstruction in one arterial branch will eventually lead to ischaemia and necrosis of the renal parenchyma supplied by this vessel.
The segmental branches of the renal undergo further divisions to supply the renal parenchyma:
Each segmental artery divides to form interlobar arteries. They are situated either side every renal pyramid.
These interlobar arteries undergo further division to form the arcuate arteries.
At 90 degrees to the arcuate arteries, the interlobular arteries arise.
The interlobular arteries pass through the cortex, dividing one last time to form afferent arterioles.
The afferent arterioles form a capillary network, the glomerulus, where filtration takes place. The capillaries come together to form the efferent arterioles.
In the outer two-thirds of the renal cortex, the efferent arterioles form what is a known as a peritubular network, supplying the nephron tubules with oxygen and nutrients. The inner third of the cortex and the medulla are supplied by long, straight arteries called vasa recta.
Fig 4 – Arterial and venous supply to the kidneys.
Fig 5 – Arterial supply to the kidney can be divided into five segments.
Clinical Relevance: Variation in Arterial Supply to the Kidney
The kidneys present a great variety in arterial supply; these variations may be explained by the ascending course of the kidney in the retroperitoneal space, from the original embryological site of formation (pelvis) to the final destination (lumbar area). During this course, the kidneys are supplied by consecutive branches of the iliac vessels and the aorta.
Usually the lower branches become atrophic and vanish while new, higher ones supply the kidney during its ascent. Accessory arteries are common (in about 25% of patients). An accessory artery is any supernumerary artery that reaches the kidney. If a supernumerary artery does not enter the kidney through the hilum, it is called aberrant.
Fig 6- Supernumerary arteries of the kidney,
Venous Drainage
The kidneys are drained of venous blood by the left and right renal veins. They leave the renal hilum anteriorly to the renal arteries, and empty directly into the inferior vena cava.
As the vena cava lies slightly to the right, the left renal vein is longer, and travels anteriorly to the abdominal aorta below the origin of the superior mesenteric artery. The right renal artery lies posterior to the inferior vena cava.
Lymphatics
Lymph from the kidney drains into the lateral aortic (or para-aortic) lymph nodes, which are located at the origin of the renal arteries.
Clinical Relevance: Congenital Abnormalities of the Kidneys
Pelvic Kidney
In utero, the kidneys develop in the pelvic region and ascend to the lumbar retroperitoneal area. Occasionally, one of the kidneys can fail to ascend and remains in the pelvis – usually at the level of the common iliac artery.
Horseshoe Kidney
A horseshoe kidney (also known as a cake kidney or fused kidney) is where the two developing kidneys fuse into a single horseshoe-shaped structure.
This occurs if the kidneys become too close together during their ascent and rotation from the pelvis to the abdomen – they become fused at their lower poles (the isthmus) and consequently become ‘stuck’ underneath the inferior mesenteric artery.
This type of kidney is still drained by two ureters (although the pelvices and ureters remain anteriorly due to incomplete rotation) and is usually asymptomatic, although it can be prone to obstruction.
Clinical Relevance - Renal Cell Carcinoma
The kidney is often the site of tumor development, most commonly renal cell carcinoma.
Due to the segmental vascular supply of the kidney it is often feasible to ligate the relative arteries and veins and remove the tumour with a safe zone of healthy surrounding parenchyma (partial nephrectomy) without removing the entire kidney or compromising its total vascular supply by ischaemia.
The kidneys are bilateral bean-shaped organs, reddish-brown in colour and located in the posterior abdomen. Their main function is to filter and excrete waste products from the blood. They are also responsible for water and electrolyte balance in the body.
Metabolic waste and excess electrolytes are excreted by the kidneys to form urine. Urine is transported from the kidneys to the bladder by the ureters. It leaves the body via the urethra, which opens out into the perineum in the female and passes through the penis in the male.
In this article we shall look at the anatomy of the kidneys – their anatomical position, internal structure and vasculature.
Fig 1 – Overview of the urinary tract.
Anatomical Position
The kidneys lie retroperitoneally (behind the peritoneum) in the abdomen, either side of the vertebral column.
They typically extend from T12 to L3, although the right kidney is often situated slightly lower due to the presence of the liver. Each kidney is approximately three vertebrae in length.
The adrenal glands sit immediately superior to the kidneys within a separate envelope of the renal fascia.
Kidney Structure
The kidneys are encased in complex layers of fascia and fat. They are arranged as follows (deep to superficial):
Renal capsule – tough fibrous capsule.
Perirenal fat – collection of extraperitoneal fat.
Renal fascia (also known as Gerota’s fascia or perirenal fascia) – encloses the kidneys and the suprarenal glands.
Pararenal fat – mainly located on the posterolateral aspect of the kidney.
Fig 2 – The external coverings of the kidney.
Internally, the kidneys have an intricate and unique structure. The renal parenchyma can be divided into two main areas – the outer cortex and inner medulla. The cortex extends into the medulla, dividing it into triangular shapes – these are known as renal pyramids.
The apex of a renal pyramid is called a renal papilla. Each renal papilla is associated with a structure known as the minor calyx, which collects urine from the pyramids. Several minor calices merge to form a major calyx. Urine passes through the major calices into the renal pelvis, a flattened and funnel-shaped structure. From the renal pelvis, urine drains into the ureter, which transports it to the bladder for storage.
The medial margin of each kidney is marked by a deep fissure, known as the renal hilum. This acts as a gateway to the kidney – normally the renal vessels and ureter enter/exit the kidney via this structure.
Fig 3 – The internal structure of the kidney.
Anatomical Relations
The kidneys sit in close proximity to many other abdominal structures which are important to be aware of clinically:
Anterior | Posterior | |
Left | Suprarenal gland Spleen Stomach Pancreas Left colic flexure Jejunum | Diaphragm 11th and 12th ribs Psoas major, quadratus lumborum and transversus abdominis Subcostal, iliohypogastric and ilioinguinal nerves |
Right | Suprarenal gland Liver Duodenum Right colic flexure | Diaphragm 12th rib Psoas major, quadratus lumborum and transversus abdominis Subcostal, iliohypogastric and ilioinguinal nerves |
Arterial Supply
The kidneys are supplied with blood via the renal arteries, which arise directly from the abdominal aorta, immediately distal to the origin of the superior mesenteric artery. Due to the anatomical position of the abdominal aorta (slightly to the left of the midline), the right renal artery is longer, and crosses the vena cava posteriorly.
The renal artery enters the kidney via the renal hilum. At the hilum level, the renal artery forms an anterior and a posterior division, which carry 75% and 25% of the blood supply to the kidney, respectively. Five segmental arteries originate from these two divisions.
The avascular plane of the kidney (line of Brodel) is an imaginary line along the lateral and slightly posterior border of the kidney, which delineates the segments of the kidney supplied by the anterior and posterior divisions. It is an important access route for both open and endoscopic surgical access of the kidney, as it minimises the risk of damage to major arterial branches.
Note: The renal artery branches are anatomical end arteries – there is no communication between vessels. This is of crucial importance; as trauma or obstruction in one arterial branch will eventually lead to ischaemia and necrosis of the renal parenchyma supplied by this vessel.
The segmental branches of the renal undergo further divisions to supply the renal parenchyma:
Each segmental artery divides to form interlobar arteries. They are situated either side every renal pyramid.
These interlobar arteries undergo further division to form the arcuate arteries.
At 90 degrees to the arcuate arteries, the interlobular arteries arise.
The interlobular arteries pass through the cortex, dividing one last time to form afferent arterioles.
The afferent arterioles form a capillary network, the glomerulus, where filtration takes place. The capillaries come together to form the efferent arterioles.
In the outer two-thirds of the renal cortex, the efferent arterioles form what is a known as a peritubular network, supplying the nephron tubules with oxygen and nutrients. The inner third of the cortex and the medulla are supplied by long, straight arteries called vasa recta.
Fig 4 – Arterial and venous supply to the kidneys.
Fig 5 – Arterial supply to the kidney can be divided into five segments.
Clinical Relevance: Variation in Arterial Supply to the Kidney
The kidneys present a great variety in arterial supply; these variations may be explained by the ascending course of the kidney in the retroperitoneal space, from the original embryological site of formation (pelvis) to the final destination (lumbar area). During this course, the kidneys are supplied by consecutive branches of the iliac vessels and the aorta.
Usually the lower branches become atrophic and vanish while new, higher ones supply the kidney during its ascent. Accessory arteries are common (in about 25% of patients). An accessory artery is any supernumerary artery that reaches the kidney. If a supernumerary artery does not enter the kidney through the hilum, it is called aberrant.
Fig 6- Supernumerary arteries of the kidney,
Venous Drainage
The kidneys are drained of venous blood by the left and right renal veins. They leave the renal hilum anteriorly to the renal arteries, and empty directly into the inferior vena cava.
As the vena cava lies slightly to the right, the left renal vein is longer, and travels anteriorly to the abdominal aorta below the origin of the superior mesenteric artery. The right renal artery lies posterior to the inferior vena cava.
Lymphatics
Lymph from the kidney drains into the lateral aortic (or para-aortic) lymph nodes, which are located at the origin of the renal arteries.
Clinical Relevance: Congenital Abnormalities of the Kidneys
Pelvic Kidney
In utero, the kidneys develop in the pelvic region and ascend to the lumbar retroperitoneal area. Occasionally, one of the kidneys can fail to ascend and remains in the pelvis – usually at the level of the common iliac artery.
Horseshoe Kidney
A horseshoe kidney (also known as a cake kidney or fused kidney) is where the two developing kidneys fuse into a single horseshoe-shaped structure.
This occurs if the kidneys become too close together during their ascent and rotation from the pelvis to the abdomen – they become fused at their lower poles (the isthmus) and consequently become ‘stuck’ underneath the inferior mesenteric artery.
This type of kidney is still drained by two ureters (although the pelvices and ureters remain anteriorly due to incomplete rotation) and is usually asymptomatic, although it can be prone to obstruction.
Clinical Relevance - Renal Cell Carcinoma
The kidney is often the site of tumor development, most commonly renal cell carcinoma.
Due to the segmental vascular supply of the kidney it is often feasible to ligate the relative arteries and veins and remove the tumour with a safe zone of healthy surrounding parenchyma (partial nephrectomy) without removing the entire kidney or compromising its total vascular supply by ischaemia.
Anatomy bladder
The bladder is an organ of the urinary system. It plays two main roles:
Temporary storage of urine – the bladder is a hollow organ with distensible walls. It has a folded internal lining (known as rugae), which allows it to accommodate up to 400-600ml of urine in healthy adults.
Assists in the expulsion of urine – the musculature of the bladder contracts during micturition, with concomitant relaxation of the sphincters.
In this article, we shall look at the anatomy of the bladder – its shape, vasculature and neurological control.
Fig 1 – Overview of the urinary tract.
Shape of the Bladder
The appearance of the bladder varies depending on the amount of urine stored. When full, it exhibits an oval shape, and when empty it is flattened by the overlying bowel.
The external features of the bladder are:
Apex – located superiorly, pointing towards the pubic symphysis. It is connected to the umbilicus by the median umbilical ligament (a remnant of the urachus).
Body – main part of the bladder, located between the apex and the fundus
Fundus (or base) – located posteriorly. It is triangular-shaped, with the tip of the triangle pointing backwards.
Neck – formed by the convergence of the fundus and the two inferolateral surfaces. It is continuous with the urethra.
Urine enters the bladder through the left and right ureters, and exits via the urethra. Internally, these orifices are marked by the trigone – a triangular area located within the fundus.
In contrast to the rest of the internal bladder, the trigone has smooth walls (this is explained by the different embryological origin: the trigone is developed by the integration of two mesonephric ducts at the base of the bladder).
Fig 2 – Anatomical features of the bladder.
Musculature
The musculature of the bladder plays a key role in the storage and emptying of urine.
In order to contract during micturition, the bladder wall contains specialised smooth muscle – known as detrusor muscle. Its fibres are orientated in multiple directions, thus retaining structural integrity when stretched. It receives innervation from both the sympathetic and parasympathetic nervous systems.
The fibers of the detrusor muscle often become hypertrophic (presenting as prominent trabeculae) in order to compensate for increased workload of the bladder emptying. This is very common in conditions that obstruct the urine outflow such as benign prostatic hyperplasia.
There are also two muscular sphincters located in the urethra:
Internal urethral sphincter:
Male – consists of circular smooth fibres, which are under autonomic control. It is thought to prevent seminal regurgitation during ejaculation.
Females – thought to be a functional sphincter (i.e. no sphincteric muscle present). It is formed by the anatomy of the bladder neck and proximal urethra.
External urethral sphincter – has the same structure in both sexes. It is skeletal muscle, and under voluntary control. However, in males the external sphincteric mechanism is more complex, as it correlates with fibers of the rectourethralis muscle and the levator ani muscle.
Fig 3 – Endoscopic view of the bladder. (A) The trigone and right ureteric orifice. (B) Prominent trabeculae of the bladder wall (hypertrophic fibers of the detrusor muscle).
Vasculature
The vasculature of the bladder is primarily derived from the internal iliac vessels.
Arterial supply is via the superior vesical branch of the internal iliac artery. In males, this is supplemented by the inferior vesical artery, and in females by the vaginal arteries. In both sexes, the obturator and inferior gluteal arteries may also contribute small branches.
Venous drainage is achieved by the vesical venous plexus, which empties into the internal iliac veins. The vesical plexus in males is in continuity at the retropubic space with the prostate venous plexus (plexus of Santorini), which also receives blood from the dorsal vein of the penis
Fig 4 – Arterial supply to the bladder via the superior vesical arteries.
Lymphatics
The superolateral aspect of the bladder drains into the external iliac lymph nodes. The neck and fundus drain into the internal iliac, sacral and common iliac nodes.
Nervous Supply
Neurological control is complex, with the bladder receiving input from both the autonomic (sympathetic and parasympathetic) and somatic arms of the nervous system:
Sympathetic – hypogastric nerve (T12 – L2). It causes relaxation of the detrusor muscle, promoting urine retention.
Parasympathetic – pelvic nerve (S2-S4). Increased signals from this nerve causes contraction of the detrusor muscle, stimulating micturition.
Somatic – pudendal nerve (S2-4). It innervates the external urethral sphincter, providing voluntary control over micturition.
In addition to the efferent nerves supplying the bladder, there are sensory (afferent) nerves that report to the brain. They are found in the bladder wall and signal the need to urinate when the bladder becomes full.
The Bladder Stretch Reflex
The bladder stretch reflex is a primitive spinal reflex, in which micturition is stimulated in response to stretch of the bladder wall. It is analogous to a muscle spinal reflex, such as the patella reflex.
During toilet training in infants, this spinal reflex is overridden by the higher centres of the brain, to give voluntary control over micturition.
The reflex arc:
Bladder fills with urine, and the bladder walls stretch. Sensory nerves detect stretch and transmit this information to the spinal cord.
Interneurons within the spinal cord relay the signal to the parasympathetic efferents (the pelvic nerve).
The pelvic nerve acts to contract the detrusor muscle, and stimulate micturition.
Although it is non-functional post childhood, the bladder stretch reflex needs to be considered in spinal injuries (where the descending inhibition cannot reach the bladder), and in neurodegenerative diseases (where the brain is unable to generate inhibition).
Clinical Relevance: Spinal Cord Injuries and the Bladder
The bladder has important clinical considerations when it comes to spinal cord lesions. There are two different clinical syndromes, depending on where the damage has occurred.
Reflex Bladder – Spinal Cord Transection Above T12
In this case, the afferent signals from the bladder wall are unable to reach the brain, and the patient will have no awareness of bladder filling. There is also no descending control over the external urethral sphincter, and it is constantly relaxed.
There is a functioning spinal reflex, where the parasympathetic system initiates detrusor contraction in response to bladder wall stretch. Thus, the bladder automatically empties as it fills – known as the reflex bladder.
Flaccid Bladder – Spinal Cord Transection Below T12
A spinal cord transection at this level will have damaged the parasympathetic outflow to the bladder. The detrusor muscle will be paralysed, unable to contract. The spinal reflex does not function.
In this scenario, the bladder will fill uncontrollably, becoming abnormally distended until overflow incontinence occurs.
Clinical Relevance: Urine Retention
Besides neurogenic dysfunction of the bladder, normal bladder emptying may be hampered by any form of obstruction, from the level of the bladder neck downwards. In males, the most common cause is obstruction due to prostate enlargement (BPH). Other causes include obstruction by a stone or large blood clot.
Acute retention is a medical emergency, as the bladder has a “normal” functional capacity with is pushed to the limit due to accumulation of urine in an acutely obstructed reservoir. The patient feels increasingly excruciating pain and the placement of a urinary catheter alleviates the symptoms immediately.
Chronic retention is a gradual procedure due to incomplete obstruction of the urine outflow. This leads to accumulation of residual urine in the bladder through months or even years; the bladder is therefore progressively distended in volumes that exceed 1-1.5 lt of urine.
Chronic retention is often accompanied by impairment of renal function. However no pain is usually present as the bladder is gradually stretched. Chronic retention of urine is often complicated by infections and formation of bladder stones due to urine stasis and accumulation of minerals in the urine
Fig 4 – Endoscopic view of stones in the bladder.
The bladder is an organ of the urinary system. It plays two main roles:
Temporary storage of urine – the bladder is a hollow organ with distensible walls. It has a folded internal lining (known as rugae), which allows it to accommodate up to 400-600ml of urine in healthy adults.
Assists in the expulsion of urine – the musculature of the bladder contracts during micturition, with concomitant relaxation of the sphincters.
In this article, we shall look at the anatomy of the bladder – its shape, vasculature and neurological control.
Fig 1 – Overview of the urinary tract.
Shape of the Bladder
The appearance of the bladder varies depending on the amount of urine stored. When full, it exhibits an oval shape, and when empty it is flattened by the overlying bowel.
The external features of the bladder are:
Apex – located superiorly, pointing towards the pubic symphysis. It is connected to the umbilicus by the median umbilical ligament (a remnant of the urachus).
Body – main part of the bladder, located between the apex and the fundus
Fundus (or base) – located posteriorly. It is triangular-shaped, with the tip of the triangle pointing backwards.
Neck – formed by the convergence of the fundus and the two inferolateral surfaces. It is continuous with the urethra.
Urine enters the bladder through the left and right ureters, and exits via the urethra. Internally, these orifices are marked by the trigone – a triangular area located within the fundus.
In contrast to the rest of the internal bladder, the trigone has smooth walls (this is explained by the different embryological origin: the trigone is developed by the integration of two mesonephric ducts at the base of the bladder).
Fig 2 – Anatomical features of the bladder.
Musculature
The musculature of the bladder plays a key role in the storage and emptying of urine.
In order to contract during micturition, the bladder wall contains specialised smooth muscle – known as detrusor muscle. Its fibres are orientated in multiple directions, thus retaining structural integrity when stretched. It receives innervation from both the sympathetic and parasympathetic nervous systems.
The fibers of the detrusor muscle often become hypertrophic (presenting as prominent trabeculae) in order to compensate for increased workload of the bladder emptying. This is very common in conditions that obstruct the urine outflow such as benign prostatic hyperplasia.
There are also two muscular sphincters located in the urethra:
Internal urethral sphincter:
Male – consists of circular smooth fibres, which are under autonomic control. It is thought to prevent seminal regurgitation during ejaculation.
Females – thought to be a functional sphincter (i.e. no sphincteric muscle present). It is formed by the anatomy of the bladder neck and proximal urethra.
External urethral sphincter – has the same structure in both sexes. It is skeletal muscle, and under voluntary control. However, in males the external sphincteric mechanism is more complex, as it correlates with fibers of the rectourethralis muscle and the levator ani muscle.
Fig 3 – Endoscopic view of the bladder. (A) The trigone and right ureteric orifice. (B) Prominent trabeculae of the bladder wall (hypertrophic fibers of the detrusor muscle).
Vasculature
The vasculature of the bladder is primarily derived from the internal iliac vessels.
Arterial supply is via the superior vesical branch of the internal iliac artery. In males, this is supplemented by the inferior vesical artery, and in females by the vaginal arteries. In both sexes, the obturator and inferior gluteal arteries may also contribute small branches.
Venous drainage is achieved by the vesical venous plexus, which empties into the internal iliac veins. The vesical plexus in males is in continuity at the retropubic space with the prostate venous plexus (plexus of Santorini), which also receives blood from the dorsal vein of the penis
Fig 4 – Arterial supply to the bladder via the superior vesical arteries.
Lymphatics
The superolateral aspect of the bladder drains into the external iliac lymph nodes. The neck and fundus drain into the internal iliac, sacral and common iliac nodes.
Nervous Supply
Neurological control is complex, with the bladder receiving input from both the autonomic (sympathetic and parasympathetic) and somatic arms of the nervous system:
Sympathetic – hypogastric nerve (T12 – L2). It causes relaxation of the detrusor muscle, promoting urine retention.
Parasympathetic – pelvic nerve (S2-S4). Increased signals from this nerve causes contraction of the detrusor muscle, stimulating micturition.
Somatic – pudendal nerve (S2-4). It innervates the external urethral sphincter, providing voluntary control over micturition.
In addition to the efferent nerves supplying the bladder, there are sensory (afferent) nerves that report to the brain. They are found in the bladder wall and signal the need to urinate when the bladder becomes full.
The Bladder Stretch Reflex
The bladder stretch reflex is a primitive spinal reflex, in which micturition is stimulated in response to stretch of the bladder wall. It is analogous to a muscle spinal reflex, such as the patella reflex.
During toilet training in infants, this spinal reflex is overridden by the higher centres of the brain, to give voluntary control over micturition.
The reflex arc:
Bladder fills with urine, and the bladder walls stretch. Sensory nerves detect stretch and transmit this information to the spinal cord.
Interneurons within the spinal cord relay the signal to the parasympathetic efferents (the pelvic nerve).
The pelvic nerve acts to contract the detrusor muscle, and stimulate micturition.
Although it is non-functional post childhood, the bladder stretch reflex needs to be considered in spinal injuries (where the descending inhibition cannot reach the bladder), and in neurodegenerative diseases (where the brain is unable to generate inhibition).
Clinical Relevance: Spinal Cord Injuries and the Bladder
The bladder has important clinical considerations when it comes to spinal cord lesions. There are two different clinical syndromes, depending on where the damage has occurred.
Reflex Bladder – Spinal Cord Transection Above T12
In this case, the afferent signals from the bladder wall are unable to reach the brain, and the patient will have no awareness of bladder filling. There is also no descending control over the external urethral sphincter, and it is constantly relaxed.
There is a functioning spinal reflex, where the parasympathetic system initiates detrusor contraction in response to bladder wall stretch. Thus, the bladder automatically empties as it fills – known as the reflex bladder.
Flaccid Bladder – Spinal Cord Transection Below T12
A spinal cord transection at this level will have damaged the parasympathetic outflow to the bladder. The detrusor muscle will be paralysed, unable to contract. The spinal reflex does not function.
In this scenario, the bladder will fill uncontrollably, becoming abnormally distended until overflow incontinence occurs.
Clinical Relevance: Urine Retention
Besides neurogenic dysfunction of the bladder, normal bladder emptying may be hampered by any form of obstruction, from the level of the bladder neck downwards. In males, the most common cause is obstruction due to prostate enlargement (BPH). Other causes include obstruction by a stone or large blood clot.
Acute retention is a medical emergency, as the bladder has a “normal” functional capacity with is pushed to the limit due to accumulation of urine in an acutely obstructed reservoir. The patient feels increasingly excruciating pain and the placement of a urinary catheter alleviates the symptoms immediately.
Chronic retention is a gradual procedure due to incomplete obstruction of the urine outflow. This leads to accumulation of residual urine in the bladder through months or even years; the bladder is therefore progressively distended in volumes that exceed 1-1.5 lt of urine.
Chronic retention is often accompanied by impairment of renal function. However no pain is usually present as the bladder is gradually stretched. Chronic retention of urine is often complicated by infections and formation of bladder stones due to urine stasis and accumulation of minerals in the urine
Fig 4 – Endoscopic view of stones in the bladder.
