AUTHOR AND EDITOR INFORMATION

Section 1 of 8  

• Authors and Editors
• Introduction
• Differentials
• Radiograph
• CT SCAN
• Mri
• Multimedia
• References

INTRODUCTION

Section 2 of 8  

• Authors and Editors
• Introduction
• Differentials
• Radiograph
• CT SCAN
• Mri
• Multimedia
• References

Background

Schistosomiasis is one of the most common parasitic infestations in the world and is caused by the Schistosoma genus of fluke. The form of schistosomiasis affecting the urinary tract involves Schistosoma haematobium. The other forms, Schistosoma japonicum, Schistosoma mansoni, and Schistosoma mekongi affect the gastrointestinal tract. The disease is endemic in the Middle East, India, Africa, Central America, and South America, yet it is rare in the United States.

Pathophysiology

Schistosomiasis typically affects the urinary system, especially the bladder, but ureteral involvement is found in as many as 30% of patients. The eggs of Schistosoma flukes are excreted into the urinary tract, causing an intense granulomatous reaction and subsequent calcification.

The life cycle of the schistosome begins with the passage of egg-containing urine into freshwater regions where the intermediate host is a snail. When the eggs are hatched, miracidia are produced. These penetrate the snail and eventually form into cercariae. The cercariae penetrate the skin of human hosts and are eventually carried to the liver, lymphatic system, lungs, and venous system, where the fluke matures. The flukes live and copulate in the portal vein in most individuals, except for S haematobium, which migrates to the perivesical venous plexus through the hemorrhoidal plexus.

The fluke attaches to the walls of the venous plexus by means of two suckers. The female fluke then deposits eggs into the venules of the urinary bladder wall or distal ureter. Some eggs penetrate the lumen of the bladder, but most become encapsulated in the vesical tissues, causing an inflammatory granulomatous reaction, fibrosis, foreign body reaction, and calcification of the dead ova. The eggs, not the flukes, cause tissue damage to the host. The degree of calcification is roughly correlated with the number of eggs deposited. The earliest calcification of dead eggs occurs 50-120 days after deposition. The female fluke can produce as many as 3500 eggs per day.

Frequency

United States

Schistosomiasis affecting the urinary tract is not found in the United States. Only 400,000 cases were identified in the United States in 1995.

International

Schistosomiasis is the most common cause of bladder calcification worldwide, causing as many as 56% of known calcifications in the bladder. It is endemic to the Middle East and Africa. The disease affects more than 200 million people worldwide (8% of the world population), and as many as 500-600 million people have been exposed to schistosomiasis of all kinds. Africa, Asia, and South America are the countries most affected.

Mortality/Morbidity

The most serious complication of urinary tract schistosomiasis is an increased incidence of squamous cell carcinoma of the bladder. Additional complications include urolithiasis, ascending urinary tract infection, urethral and ureteral stricture with subsequent hydronephrosis, and renal failure.

Sex

Schistosomiasis affects men more often than women, with a ratio of approximately 9:1.

Age

Schistosomiasis usually occurs in individuals younger than 30 years.

Clinical Details

Schistosomiasis typically causes a chronic low-grade infection with flulike symptoms. Clinical symptoms may include fatigue, headache, a stiff neck, a lack of energy, and neurologic symptoms due to central nervous system (CNS) complications.

Tuberculosis is the only real differential diagnosis. The propagation of both entities is different because schistosomiasis starts in the bladder and ascends, whereas tuberculosis starts in the kidney and progresses distally. In addition, the bladder is usually distensible with schistosomiasis, but it is fibrotic and limited in volume with tuberculosis.

Urologic symptoms include either microscopic or gross hematuria, dysuria, urinary frequency, and urinary urgency.

Treatment of urinary-tract schistosomiasis involves mainly 2 drugs: praziquantel and metrifonate. Oxamniquine is another medication, but it is no longer available in the United States.

DIFFERENTIALS

Section 3 of 8  

• Authors and Editors
• Introduction
• Differentials
• Radiograph
• CT SCAN
• Mri
• Multimedia
• References

Other Problems to be Considered

Tuberculosis
Primary amyloidosis
Cytostatic medications
Alkaline incrustation cystitis

RADIOGRAPH

Section 4 of 8  

• Authors and Editors
• Introduction
• Differentials
• Radiograph
• CT SCAN
• Mri
• Multimedia
• References

Findings

Calcification in the wall of the bladder or distal ureters can be identified on plain radiographs (see Image 1). Mucosal irregularity, inflammatory pseudopolyps, ureteritis cystica, ureteral dilatation and stricture, and reduced bladder capacity can be found with intravenous urography (IVU), retrograde ureterography, or cystography. However, conventional radiographs are not useful until calcifications have developed in the bladder or ureters. With regard to IVU, most of the findings are in the bladder and distal ureter because the kidneys remain normal until late in the disease.

Involvement of the ureters occurs in as many as 65% of patients. The ureters commonly have persistent filling in the lower segment; dilated ureters are another finding. Ureteral strictures can be found, and, as the disease progresses, beading of the lower ureteral segment may be observed. Subsequent ureteral fibrosis leads to calcifications of the distal ureter, which have a characteristic pattern of linear or parallel calcifications on plain radiographs. As many as 80% of the strictures occur in the bladder wall near the junction with the ureters. Dilatation of the ureter is common. This is often caused by vesicoureteric reflux, stenosis of the ureter, or an edematous ureteral wall that causes deficient peristalsis.

With regard to the bladder, indistinctness or hazy changes are caused by submucosal edema and pseudotubercles. The body forms an intense granulomatous reaction to the ova, and fibrosis ensues. This fibrosis traps the ova in the tunica propria of the bladder wall where the ova die and become calcified. The calcification is not in the fibrous tissue, but it is caused by calcified ova. The calcification spreads around the bladder wall and can completely encircle the bladder, appearing as a curvilinear ring.

A calcified area in the bladder has an estimated 500,000 to 1 million eggs per cubic centimeter. The extent of the calcification is roughly correlated with the number of eggs in the bladder lumen. The bladder wall becomes fibrotic, but it is still distensible and maintains a normal capacity.

CT SCAN

Section 5 of 8  

• Authors and Editors
• Introduction
• Differentials
• Radiograph
• CT SCAN
• Mri
• Multimedia
• References

Findings

Compared with other techniques, CT better delineates the extent of the calcifications related to schistosomiasis. Bladder calcifications are characteristically linear, coarse, or floccular in schistosomiasis. Usually, the calcifications are first seen in the base of the bladder on plain radiographs, but they more commonly appear in the anterior wall of the bladder on CT scans. The thickness of the ureteral wall is better evaluated with CT than with any other modality.

Degree of Confidence

CT scans demonstrate the calcifications better than plain radiographs, IVU images, or sonograms. CT is also helpful in the staging of bladder carcinomas.

MRI

Section 6 of 8  

• Authors and Editors
• Introduction
• Differentials
• Radiograph
• CT SCAN
• Mri
• Multimedia
• References

Degree of Confidence

CT is more sensitive than conventional radiography in the detection of calcifications.

MULTIMEDIA

Section 7 of 8  

• Authors and Editors
• Introduction
• Differentials
• Radiograph
• CT SCAN
• Mri
• Multimedia
• References

Media file 1:  Plain radiograph in a 35-year-old man with a 2-week history of hematuria, frequency, urgency, and dysuria demonstrates a calcified bladder wall.
	View Full Size Image
Media type:  X-RAY

REFERENCES

Section 8 of 8

• Authors and Editors
• Introduction
• Differentials
• Radiograph
• CT SCAN
• Mri
• Multimedia
• References

• Al-Ghorab MM, Rahman MA, El-Rifaie M. Radiologic findings of bilharzial (schistosomal) contracted bladder. Urology. Mar 1978;11(3):303-5. [Medline].
• Jorulf H, Lindstedt E. Urogenital schistosomiasis: CT evaluation. Radiology. Dec 1985;157(3):745-9. [Medline].
• Palmer PE, Reeder MM. Parasitic diseases involving the urinary tract. In: Clinical Urography, 2nd ed. 2000;1167-79.
• Webbe G. The six diseases of WHO. Schistosomiasis: some advances. Br Med J (Clin Res Ed). Oct 24 1981;283(6299):1104-6. [Medline].

Article Last Updated: Aug 23, 2002