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Imaging Diagnosis

The radiological literature on pentastomiasis is sparse and the prevalence of the parasite as detected radiologically varies greatly. In the (then) Congo, Van Wymeersch and Wanson in 1954 found only 3 cases of pentastomiasis in a review of 70,000 routine roentgenograms. Bretland in 1962 could find only 14 reported cases in the world which had been diagnosed radiographically, but these reports obviously do not reflect the true incidence of the disease.

Cockshott noted that tongue worm infestation was not an uncommon x-ray finding in certain areas of West Africa, especially Nigeria and the (then) Congo, Lindner in 1965 found 14 cases of Armillifer armillatus in a random survey of abdominal films on 1,000 patients in Nigeria: in his series, the greatest incidence (7%) occurred in men 50 to 59 years-old.

The calcified dead larvae are almost always localized to the abdomen and chest and are rarely seen elsewhere. They are always multiple and are seen more often in the upper abdomen than in the lower abdomen and thorax. The calcifications are crescentic, horseshoe or comma-shaped, or coiled when seen en face and vary from 4 to 8-mm in size. Some may appear oval or rectilinear in outline when seen end on.

They are most commonly seen in the right upper quadrant, either on or below the peritoneal surface of the liver (Figs. 28.4-28.6); however, they may be seen in abundance as scattered calcifications anywhere in the peritoneal cavity (including the spleen, mesentery and even rarely the scrotum), as well as in the lungs and pleura (Figs. 28.7 and 28.8). The calcified nymphs of A. moniliformis are slightly smaller than those of A. armillatus.

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Fig. 28.4 (A and B) Numerous calcified nymphs of Armillifer armillatus are seen throughout the liver, spleen and peritoneum on radiographs obtained as part of a small bowel series on a Nigerian. Note their characteristic coiled or C-shaped outlines. (Courtesy of Dr. Stanley Bohrer, Winston-Salem, North Carolina).

Fig. 28.5 Pentastomiasis (Armillifer armillatus) and schistosomiasis haematobium in a West African native. The coiled outlines of many small calcified nymphs are seen within and along the peritoneal surface of the liver. Right-sided hydronephrosis and hydroureter are present due to a distal ureteral stricture caused by concurrent infection with S. haematobium. (Courtesy of Dr. William Thomas, McLean, Virginia).

Fig. 28.6 Pentastomiasis (Armillifer armillatus) and calcified guinea worm (Dracunculus medinensis) in a Nigerian man. There are numerous small calcified Armillifer nymphs in the liver and peritoneal cavity, and there is the typical slender serpiginous outline of a calcified guinea worm in the subcutaneous tissues of the abdominal wall. (Courtesy of Dr. Stanley Bohrer, Winston-Salem, North Carolina).

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Fig. 28.7 (A) Pentastomiasis with innumerable tiny calcified nymphs of Armillifer (Porocephalus) moniliformis throughout the liver, spleen, mesentery and peritoneal cavity of a 55-year-old Filipino man. Most of these nymphs show the characteristic semilunar or C-shaped outline of this parasite. These were an incidental finding on the intravenous pyelogram study. (B,C) Hundreds more of these calcified nymphs are present within the lungs and pleural cavity of the same patient. (Courtesy of Dr. Howard Steinbach and Radiology).

Fig. 28.8 Pentastomiasis (Armillifer armillatus) in an African man showing multiple calcified, coiled and C-shaped nymphs within the lung and pleura. Some of the nymphs appear rectilinear in outline because they are seen end on. (Courtesy of the late Dr. Benjamin Felson, Cincinnati).

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