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Endoscopic Retrograde Cholangiography (ERCP)

ERCP is particularly useful when a hydatid cyst has ruptured into the biliary tract (Fig. 3.29). The cyst can often be localized and impacted hydatid material (daughter cysts, fragments of membranes), that may cause jaundice, can be removed at the same time.

Follow-up After Treatment

Even if there are no clinical indications, it is a wise precaution to follow up all patients who have been treated for hydatid disease. This should be done after one year and again in another two years, both to exclude local recurrence (e.g., after surgery) and the growth of new cysts elsewhere in the patient. This is particularly important if the patient's laboratory tests have changed. Seroconversion from positive to negative usually occurs within one year after successful treatment, although it may take up to four years. The tests will become positive again when there is recurrence.

Ultrasonography and a chest radiograph will demonstrate any recurrent cysts except in the skeleton or CNS. If these are suspected, appropriate bone radiography or scintigraphy and CT or MRI scanning of the spine or brain will be needed.

Clinical and Imaging Correlation for Specific Organs and Regions

Abdomen

The majority of hydatid cysts occur within the abdomen (Figs.3.56, 3.57, 3.58). The liver may harbor up to 70% of all hydatids, and various series from around the world indicate a frequency of 3-9% for cysts within the spleen, 2-4% within the kidney, and 2% to as high as 18% within the peritoneum. This wide variation in peritoneal involvement is probably a reflection of the fact that in some developing countries the primary liver cyst is not identified and treated and may eventually rupture into the peritoneum. The slow expansion of secondary cysts will in time lead the patient to medical attention.

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Fig. 3.56 Multiple hydatid cysts in the abdomen and pelvis demonstrated by CT after intravenous bolus of contrast medium in a Saudi Arabian patient. (A) Large type II hydatids with typical daughter cysts in both lobes of liver. One cyst protruding through a right intercostal space later ruptured through skin. (B) Hydatid cysts adjacent to right kidney, causing impression on the renal outline (small arrow). Small low-density lesion in left kidney represents a simple or hydatid cyst (long arrow). Ascites and free abdominal gas are also noted. (C and D) Multiple type I and II hydatids in the pelvis with and without daughter cysts. (See Fig. 3.155 which shows the results of surgery and chemotherapy in this patient.) (Courtesy of Dr. von Sinner.)

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Fig. 3.57 A 40-year-old Saudi Arabian man with multiple hydatid cysts of the abdomen. Five years previously, he noted swellings in his upper abdomen, which disappeared 2 years later after a traffic accident. A year later he again noted abdominal distention, and at surgery hundreds of small hydatids were removed from his abdomen. He underwent mebendazole therapy for 3 years with unsatisfactory results. Four months ago he presented again with new abdominal swellings, and a large smooth nontender 8 cm mass was felt in his right hypochondrium, with a smaller mass in the left hypochondrium and a third mass in the right lumbar area. In his past history there was one episode of jaundice and abdominal pain. (A) Nonenhanced abdominal CT scan revealed a large hepatic hydatid cyst with a defective posterior cyst wall (white arrows) with a low-intensity rim (black arrows), suggesting possible imminent rupture. Three weeks later, an ultrasound study (B) of the right abdomen revealed the "serpent or snake sign" of detached parasitic membranes pathognomonic for hydatid disease, showing the cyst wall (black arrow) and collapsed membranes (white arrow). (C) At the same time, a T1-weighted axial MR image, right side (TR 850 ms, TE 20 ms) and (D) T2-weighted axial MR image (TR 2000 ms, TE 100 ms) demonstrated the "serpent or snake sign" of detached membranes (arrows). Following surgery, the patient made an uneventful recovery. (Courtesy of Dr. von Sinner and Eur J Rad, 1990.)

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Fig. 3.58 (A and B) Multiple type I and II hydatid cysts of the liver and spleen as seen on CT scans in 2 Saudi Arabian patients. In (B), a 10-year-old boy, the hydatids of the left lobe of the liver and of the spleen (arrows) lie in close relationship to the barium-filled stomach. There is faint calcification in the wall of the splenic cyst. (Courtesy of Dr. von Sinner and Eur J Rad, 1990.)

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