Passing gas (air) in the urine, a rare symptom, usually indicates an abnormal opening (fistula) between the urinary tract and the intestine, which normally contains gas. A fistula may be a complication of diverticulitis Diverticulitis Diverticulitis is inflammation of one or more balloon-like sacs (diverticula). Infection may or may not develop. Diverticulitis usually affects the large intestine (colon). Left lower abdominal... read more 
, other types of intestinal inflammation, an abscess, or cancer. A fistula between the bladder and the vagina may also cause gas to escape into the urine. Rarely, certain bacteria in the urine may produce gas.
Doctors do a pelvic examination in affected women. To diagnose fistulas, doctors may insert a flexible viewing tube into the bladder (cystoscopy Cystoscopy A doctor can diagnose some disorders of the bladder and urethra (for example, bladder tumors, stones in the bladder, benign prostatic enlargement) by looking through a flexible viewing tube... read more ) or colon (sigmoidoscopy Endoscopy Endoscopy is an examination of internal structures using a flexible viewing tube (endoscope). In addition to examinations, doctors can use endoscopy to do biopsies and give treatment. Endoscopes... read more ), or both. Sometimes imaging tests, such as computed tomography Computed tomography There are a variety of tests that can be used in the evaluation of a suspected kidney or urinary tract disorder. (See also Overview of the Urinary Tract.) X-rays are usually not helpful in evaluating... read more (CT), magnetic resonance imaging Magnetic resonance imaging There are a variety of tests that can be used in the evaluation of a suspected kidney or urinary tract disorder. (See also Overview of the Urinary Tract.) X-rays are usually not helpful in evaluating... read more (MRI), or ultrasonography Ultrasound Scanning (Ultrasonography) of the Abdomen Ultrasound scanning uses sound waves to produce pictures of internal organs (see also Ultrasonography). An ultrasound scan can show the size and shape of many organs, such as the liver and pancreas... read more 
, are done.
Fistulas are usually repaired surgically.
(See also Overview of Urinary Tract Symptoms Overview of Urinary Tract Symptoms Kidney and urinary tract disorders can involve one or both kidneys, one or both ureters, the bladder, or the urethra, and in men, the prostate, one or both testes, or the epididymis. Problems... read more .)
