Overview

• A common congenital anomaly of the urinary bladder that occurs when a portion of the urachus (i.e., a fetal conduit that allows passage of urine from the bladder to the placenta) located at the bladder vertex fails to close; the result is a blind diverticulum of variable size that protrudes from the bladder vertex.
• Other characteristics include congenital microscopic diverticula (microscopic lumens that may persist at the bladder vertex).
• Acquired macroscopic diverticula develop after the onset of concurrent but unrelated acquired lower urinary tract diseases; presumably, urethral obstruction or detrusor hyperactivity induced by inflammation causes high intraluminal pressure and subsequent enlargement of microscopic diverticula.
• Congenital macroscopic diverticula, most likely caused by impaired urine outflow, develop before or soon after birth and persist indefinitely.

Signalment

• Dog and cat.
• Frequently encountered in cats with acquired lower urinary tract diseases; twice as common in male cats as in female cats.
• No breed or age predisposition.

Signs

• Depend on concomitant disorders predisposing to formation of macroscopic vesicourachal diverticula.
• Hematuria, dysuria, pollakiuria, or signs of urethral obstruction in some patients with concurrent acquired lower urinary tract diseases.

Causes & Risk Factors

• Persistent congenital microscopic diverticula-cause unknown.
• Congenital microscopic diverticula-risk factors for acquired macroscopic diverticula.
• Diseases associated with increased bladder intraluminal pressure (e.g., bacterial urinary tract infection, uroliths, urethral plugs, and idiopathic disease)-risk factors for acquired macroscopic diverticula.

Differential Diagnosis

• Persistent (or patent) urachus; very uncommon)-characterized by inappropriate loss of urine through the umbilicus.
• Persistent urachal ligaments are non-patent fibrous remnants of the urachus, connecting the bladder vertex to the umbilicus.
• Urachal cysts are focal accumulations of fluid in isolated segments of the urachus. They may be aseptic or septic.

CBC/Biochemistry/Urinalysis

• Abnormal findings are related to the underlying disorder that causes vesicourachal diverticula, unless complicated by concurrent acquired lower urinary tract diseases.
• Abnormal findings related to secondary urinary tract infection.

Imaging

• Congenital and acquired macroscopic diverticula-best identified by positive-contrast urethrocystography.
• Radiographs obtained with the bladder completely then partially distended with contrast medium may facilitate detection of small diverticula.

Diagnostic Procedures

N/A

Pathologic Findings

• Extramural macroscopic diverticula appear as convex or conical luminal projections from the bladder vertex.
• Intramural microscopic diverticula appear as transitional epithelium-lined lumens persisting at the bladder vertex from the level of the submucosa to subserosa.

Drug(s)

N/A

Patient Monitoring

If bacterial urinary tract infection persists or recurs despite proper antimicrobial therapy, the status of the diverticulum should be reevaluated by contrast radiography.

Prevention/Avoidance

Avoid diagnostic procedures or treatments that alter normal host urinary tract defenses and predispose to urinary tract infection.

Possible Complications

Persistent congenital macroscopic diverticula are risk factors for recurrent bacterial urinary tract infection.

Expected Course and Prognosis

• Congenital microscopic diverticula are usually clinically silent unless complicated by concurrent lower urinary tract disease.
• Acquired macroscopic diverticula typically heal in 2–3 weeks after amelioration of clinical signs of lower urinary tract disease.
• Diverticulectomy and appropriate antimicrobial therapy usually associated with resolution of recurrent urinary tract infections in patients with persistent congenital macroscopic diverticula.

Associated Conditions

• Persistent congenital macroscopic diverticula are potential risk factors for recurrent bacterial urinary tract infections.
• Acquired macroscopic diverticula are typically encountered in patients with concurrent lower urinary tract diseases.

See Also

• Feline Idiopathic Lower Urinary Tract Disease
• Lower Urinary Tract Infection chapters