What causes air to be present in the urine during voiding?

Air with Urinary Voiding: Causes

Pneumaturia (air in the urine during voiding) is most commonly caused by a fistula between the gastrointestinal tract and urinary bladder, typically from diverticulitis, colon cancer, or Crohn's disease, and requires urgent diagnostic evaluation as outcomes can be serious or fatal if untreated. 1

Primary Pathological Causes

The presence of air during urination represents a pathological communication or gas-producing infection that demands immediate investigation:

Fistulous Connections (Most Common)

• Colovesical fistula from diverticular disease is the leading cause, where inflamed bowel creates an abnormal connection to the bladder 1
• Malignancy (particularly colon cancer) eroding into the bladder wall 1
• Inflammatory bowel disease (Crohn's disease) creating entero-vesical fistulas 1
• Post-surgical or post-radiation fistulas 1

Gas-Producing Infections

• Emphysematous cystitis from gas-forming bacteria (typically E. coli or Klebsiella) in diabetic or immunocompromised patients 1
• This presents with air in the bladder wall itself, not just the lumen 1

Iatrogenic Causes

• Recent instrumentation or catheterization introducing air 1
• Post-cystoscopy or urodynamic studies 1

Critical Diagnostic Approach

Pneumaturia is a rare phenomenon in the general population but more frequent in defined high-risk subgroups, and relevant symptoms may be hardly noticeable for a relatively long period despite serious underlying pathology. 1

High-Risk Patient Populations

• Patients with known diverticular disease 1
• History of pelvic malignancy or radiation 1
• Diabetic patients (risk for emphysematous infection) 1
• Inflammatory bowel disease patients 1

Essential Workup

• Urine culture to identify gas-forming organisms and rule out emphysematous cystitis 1
• CT cystography or CT abdomen/pelvis with contrast to identify fistulous tracts and air in bladder wall 1
• Cystoscopy to visualize the fistula opening and rule out bladder pathology 1
• Colonoscopy to identify the bowel source if fistula suspected 1

Important Clinical Caveats

The outcome of untreated pneumaturia may be serious and sometimes fatal, requiring diagnostic alertness despite potentially subtle initial presentation. 1

• Pneumaturia is NOT related to dysfunctional voiding patterns (staccato flow, incomplete emptying) which involve pelvic floor dyssynergia but not air passage 2
• Do not confuse with "bubbles" from vigorous voiding or proteinuria, which appear as foam rather than distinct gas 1
• Fecaluria (fecal matter in urine) or recurrent polymicrobial UTIs strongly suggest colovesical fistula 1
• Delay in diagnosis allows progression of underlying pathology (abscess, sepsis, or malignancy spread) 1