Instrumental imaging methods
Specific radiological examinations, as well as ultrasound, CT, and MRI, are used to evaluate the lower urinary tract. The choice of method depends strictly on the clinical objective.
- Conventional radiography (CR): Characterized by low cost and availability, but has severe limitations. Its sensitivity for urolithiasis is only about 60% and depends on calculus density. The method is useless for detecting malignant tumors, as calcification rarely occurs in renal cell carcinoma or transitional cell carcinoma.
- Intravenous urography (IVU): Involves the administration of non-ionic contrast (bolus or drip) followed by a series of images. The standard protocol includes a scout radiogram, 1-minute tomograms, 5-minute images with compression of the pelvic ureters, and 10–20 minute images. The examination concludes with an evaluation of the bladder before and after voiding. Today, this method is gradually being replaced by CT; however, digital tomosynthesis improves urogram quality and reduces radiation dose by 56%.
- Voiding cystourethrography (VCUG): The gold standard for detecting vesicoureteric reflux (vesicoureteric reflux) and urethral malformations.
- Retrograde urography: Performed by administering contrast through a catheter during cystoscopy. Rarely used, mainly for complex tasks involving ambiguous filling defects or post-lithotripsy evaluation.
Congenital bladder anomalies
Bladder anomalies are diverse and frequently combined with malformations of other systems.
- Bladder agenesis: A rare pathology associated with impaired anterior cloaca formation. Accompanied by ectopic ureteral insertion.
- Bladder and urethral duplication: Occurs when a muscular septum forms (involving the detrusor), usually in the sagittal plane. Frequently associated with duplication of the external genitalia.
- Diverticula: Outpouchings of the bladder wall. These include Hutch diverticulum (Hutch diverticulum), located at the vesicoureteric junction and predisposing to reflux, as well as «bladder ear» (bladder ear), a diverticulum herniating into the internal inguinal ring. Congenital forms may be asymptomatic, but are prone to infections and stone formation.
- Prune-belly syndrome (Prune-belly syndrome): The classic triad includes absence of the abdominal rectus muscles, ureteral dilation with prostatic urethral enlargement, and bilateral cryptorchidism. The bladder wall is thickened due to connective tissue, but lacks trabeculation.
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Urachal pathologies
The urachus is the embryonic median umbilical ligament. Failure of its obliteration leads to the formation of remnant structures:
- Urachal cyst (urachal cyst): Formed when the umbilical and vesical ends close, but the central segment remains open.
- Urachal sinus (urachal sinus): A blind tract opening at the umbilicus.
- Urachal diverticulum: A portion of the duct that maintains communication with the bladder lumen.
- Malignant tumors: Urachal remnant adenocarcinoma produces mucin, may calcify, and carries a worse prognosis compared to typical bladder cancer. Urachal anomalies are most commonly complicated by infection.
Urethral malformations and strictures
Visualization of the urethra is of key importance for identifying the causes of impaired urine outflow.
- Posterior urethral valves (posterior urethral valves): Formed from elements of the Wolffian duct. A mucosal fold extends from the verumontanum to the prostatic urethra, causing obstruction. This leads to hypertrophy of the bladder wall (trabeculation) and bilateral hydronephrosis. On voiding cystourethrography images, the posterior urethra appears dilated.
- Megalourethra (megalourethra): Arises due to developmental defects of the corpora cavernosa or corpus spongiosum of the penis. When only the corpus spongiosum is underdeveloped, the urethra acquires a navicular shape, and with combined underdevelopment of both structures, a fusiform shape.
- Strictures and diverticula: Ventrally located diverticula of the anterior urethra or congenital strictures (most commonly at the junction of the anterior and posterior segments) frequently cause marked obstruction.
Briefly: answers to topical questions
What congenital anomalies of the urinary bladder exist?
Congenital anomalies of the bladder include a wide spectrum of developmental malformations, ranging from agenesis to complex syndromes. The following main pathologies are distinguished:
- Bladder agenesis (Bladder agenesis) — an extremely rare pathology of unclear origin in which the ureters insert ectopically.
- Duplication of the bladder and urethra (Duplication of the bladder and urethra) — division of the bladder by a septum, frequently associated with renal obstruction.
- Bladder diverticula (Bladder diverticula) — congenital outpouchings of the wall, including the Hutch diverticulum (Hutch diverticulum) and the bladder ear (Bladder ear).
- Prune-belly syndrome (Prune-belly syndrome) — a syndrome comprising the absence of the rectus abdominis muscles, cryptorchidism, and urinary tract anomalies.
- Bladder exstrophy – epispadias – cloacal exstrophy complex — closure defects of the abdominal wall with protrusion of the anterior bladder wall.
- Urachal anomalies (Urachus) — cysts, sinuses, and diverticula of the urachus remnant.
What are the grades of vesicoureteral reflux according to voiding cystourethrography?
According to voiding cystourethrography, there are 5 grades of severity of vesicoureteral reflux, the classification of which is based on the height of urine ascent and the degree of urinary tract dilatation:
- Grade I — reflux is confined to the ureter only, urine ascent does not reach the renal pelvis, no dilatation.
- Grade II — total reflux (urine reaches the renal pelvis and calyces), but no dilation of the ureter and pelvicalyceal system is observed, renal calyceal fornices retain their sharp shape.
- Grade III — mild or moderate dilation of the ureter and renal pelvis, blunting of the calyceal fornices begins.
- Grade IV — marked dilatation and tortuosity of the ureter, the pelvis and calyces are significantly dilated, fornices are rounded, but papillary contours are still traceable.
- Grade V — end-stage with marked dilation and tortuosity of the ureter, severe dilatation of the pelvicalyceal system, and clubbing of the calyces without visualization of the papillae.
What radiologic signs are characteristic of bladder cancer?
The following radiologic signs are described for bladder cancer:
- CT: urothelial carcinoma may be visualized as a contrast-enhancing nodular mass arising from the bladder wall and projecting into its lumen. On early contrast-enhanced CT, a large lobulated, tuberous mass causing thickening of the bladder wall is described. In the excretory phase of CT urography, transitional cell carcinoma may be defined as a filling defect in the bladder lumen. Irregular wall thickening and prominent circular thickening of the bladder wall are also described.
- Calcifications: detected in approximately 5% of bladder cancer cases; small areas of calcification may be identified within the tumor structure.
- MRI: on T1-weighted images, the tumor has a soft-tissue signal intensity similar to the normal bladder wall; on T2-weighted images, the signal is intermediate—between the hyperintense signal of urine and the hypointense signal of the normal wall.
- MRI enhancement: characterized by rapid and intense gadolinium-based contrast agent uptake.
How to memorize
To remember the triad of the Prune-belly (Eagle-Barrett) syndrome, use the rule of three "M's": Muscles (absent on the abdominal wall) — Ureters (dilated) — Scrotum (empty due to cryptorchidism).
Class and exam questions
What is the essence of the "drooping lily" sign?
This is a radiological phenomenon seen on a voiding cystourethrogram (VCUG). It occurs in renal duplication, when a hydronephrotically dilated upper segment (without contrast) displaces the contrasted lower segment inferiorly.
Why is ureteral compression used during intravenous urography?
Compression of the pelvic ureters helps to better fill the upper urinary tract with contrast. This facilitates the detection of small tumors and signs of papillary necrosis.
Which diagnostic imaging method is preferred when posterior urethral valves are suspected?
Voiding cystourethrogram (VCUG). The images reveal elongation and dilation of the posterior urethra, even if the valve leaflets themselves cannot be visualized.
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What else to study on this topic
- Cloacal malformations and cloacal exstrophy
- Ormond's disease (retroperitoneal fibrosis) and ureteral deviation
- Anomalies of Cowper's glands
- Retrocaval ureter: CT findings
- Variants of urethral duplication (including Y-shaped configuration)
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Other topics in the section "Diagnostic Radiology of the Abdominal Organs"
Renal agenesisRadiation anatomy of the kidneysRadiation anatomy of the urethraAnomalies of position and structure of the kidneys and uretersIntravenous urographyComputed tomography urographyMagnetic resonance urography
Entire section "Diagnostic Radiology of the Abdominal Organs"Prepared by WhiteCoat Pro faculty in accordance with the medical school curriculum. For educational purposes only.