Liver

The hepatic changes of schistosomiasis japonica are characteristic (Figs. 2.45-2.53): rarely, similar changes may be found in other schistosomal infections. The background picture of periportal fibrosis is similar to S. mansoni infections, but the extent of hepatic calcification is quite different (Figs. 2.45-2.47).

Occasionally on plain radiographs, but especially on CT scanning the pattern of the calcified eggs can be capsular or septal. Although described as "capsular" the eggs are actually subcapsular and may be arranged in a linear pattern all around the liver (Fig. 2.51). Within the septa, there is similar calcification, and the pattern has been described as a network or "turtleback" appearance (Fig. 2.50). The septal pattern, in particular, enhances on CT performed following contrast administration (Figs. 2.48, 2.49).

Another characteristic pattern is irregularity of the liver outline, caused by notching (Figs. 2.48-2.51). Where the focal fibrosis in the capsule joins the fibrosis in the septa, there is depression, macroscopically resembling a star or furrows if the retraction is sufficient. This notching has not been seen so clearly in any other schistosomal infection.

The third pattern is nodular, within the liver parenchyma. These macronodules, also due to fibrosis in the portal spaces, can be mistaken for macronodular cirrhosis or even metastases (Fig. 2.45).

Ultrasonography shows an echogenic network, and branching of the hyper- reflective septa should be sought. Enclosed within these echogenic septa will be polygonal areas of apparently normal liver. When the fibrosis is incomplete, it causes a moderately fine sieve-like appearance. The fully developed septal changes in schistosomiasis japonica on ultrasound are described as being a fish-scale or retiform pattern and may be found in 30% of patients, particularly those who have a high antibody titer (Fig. 2.50). The irregular notched surface of the liver can also be demonstrated by ultrasonography.

Although periportal fibrosis occurs in any type of schistosomiasis, in S. japonicum infections there is usually atrophy of the right lobe of the liver and some hypertrophy of the left and caudate lobes. This is another useful finding on either CT or ultrasonography (Figs. 2.50, 2.51).

There is an association of hepatic carcinoma with S. japonicum infections; it is possible that this is due to the increased incidence of hepatitis B infection, because carcinomas occur more commonly in mild schistosomiasis rather than in advanced cases. The tumors have been described as large, solitary, and nodular in pattern; some are even massive. Other patients may have multiple nodules. Differentiation may be possible by CT or MRI, but guided needle biopsy is usually required. In some series, there has been an increase in carcinoma of the stomach and even the duodenum, but whether this is a significant link is not yet established.

Although the imaging pattern of periportal fibrosis is easily recognizable, it is not entirely unique to schistosomiasis. Prominent periportal echogenicity occurs in patients with recurrent pyogenic cholangitis, rarely in acute cholecystitis and occasionally in hepatocellular carcinoma.

Recurrent (oriental) cholangitis has a distinct history of fevers, and there will be dilatation of the intra- and extrahepatic ducts, often containing debris (see Chapter 21). In hepatocellular carcinoma the periportal echogenicity is predominantly vascular and can be imaged with MRI or angiography. In cholecystitis the cause is probably inflammatory and may be reversible.

Accompanying the hepatomegaly, there is often splenomegaly and, in many patients, ascites. The pattern of vascular collaterals, including esophageal varices, is very similar to those that develop in S. mansoni infections. Thickening of the wall of the gallbladder can occur and may go on to fibrosis. There are seldom any biliary calculi or polyps. The assessment of portal hypertension is the same as for S. mansoni.

Lungs

The radiological findings in the lungs of patients with S. japonicum infections are very similar to those of S. mansoni. In many patients the chest radiograph appears normal and will remain so. In the acute stage, the pattern of the Katayama syndrome occurs; indeed it was first described with S. japonicum infection. There is an increase in the pulmonary vascular and interstitial markings and enlargement of the hilar lymph nodes.

The lung changes may progress to fibrosis and occasionally scattered nodular calcification. As with other varieties of schistosomiasis, emphysema is not a major factor. In some patients S. japonicum infections progress to eventual pulmonary hypertension and dilatation of the pulmonary arteries as occurs in S. mansoni infections, following the same pathological and radiological pattern.

Central Nervous System

Schistosomiasis in the central nervous system is asymptomatic in the majority of patients. Multiple ova and evidence of immune complex reaction, with small granulomas in some cases, may be found at autopsy but without clinically localizing signs.

The brain and spinal cord may be infected in all three varieties of schistosomiasis, but perhaps most frequently with S. japonicum.

Acute CNS Infection

At the Katayama (acute) stage, cerebral infection presents with convulsions and seizures, with or without loss of consciousness. The clinical picture may resemble Jacksonian epilepsy with an abnormal electroencephalogram, or intracerebral hemorrhage. Other patients will present with paraplegia, which may be severe or mild, complete or incomplete, usually in the thoracic or lower lumbar area. The differential diagnosis may be confusing. The history of exposure to infected water a few weeks previously is very important. There is usually an accompanying fever, cough and sometimes urticaria, symptoms which are not usual with other cerebral or spinal illnesses. In this early (Katayama) stage, there may be no eggs in the stools and the serology may be negative. The patients may recover completely without specific antischistosomal therapy (although the cerebral swelling may need treatment). After a few months there may be eggs in the stool, the serology becomes positive and, if there is any doubt, liver biopsy will provide further evidence.

Computed tomography (and MRI) have shown large multifocal areas of low density or low signal intensity, with periventricular lucencies which enhance on contrast CT examinations. There may be a mass effect and raised intracranial pressure. There may be a similar mass effect in the spinal cord.