Prepared by Stuart E. Mirvis, MD, Professor of Radiology, University of Maryland Medical School, Baltimore, MD.

PROBLEM:

A 6-year-old girl presented to the emergency department with vomiting and severe left upper and mid-abdominal pain. A mass was palpated on physical examination. The patient had a several month history of intermittent abdominal pain. An abdomino-pelvic CT scan was obtained after administration of oral and intravenous contrast material. Four CT images (figures1-4) from that study are provided. What is the most likely diagnosis?

ANSWER: "Wandering spleen" with pedicle torsion and infarction

DISCUSSION:

Wandering spleen is an uncommon condition that usually presents clinically in children of 3 months to 10 years of age (most typically in children who are less than 1 year old). The condition is a result of congenital abnormal development of the dorsal mesogastrium. Normally, the spleen and its ligamentous attachments, the lienorenal and gastrolienal ligaments, are derived from the dorsal mesogastrium. The posterior leaf of the dorsal mesogastrium fuses with the parietal peritoneum anterior to the left kidney to form the lienorenal ligament, the most important stabilizer of splenic position. Failure or incomplete fusion of these structures allows for abnormal mobility of the spleen related to a long splenic vascular pedicle that permits excessive intraperitoneal movement of the spleen. It is the long vascular pedicle which permits torsion of the spleen to occur, leading to ischemia. In addition, a portion of the pancreatic tail is derived from the dorsal mesogastrium and may also be involved in torsion.

Clinically, a patient may present with acute, chronic, or intermittent abdominal symptoms. Intermittent pain may result from torsion and spontaneous detorsion of the spleen, while an acute abdomen would result from prolonged vascular pedicle torsion and infarction. Associated symptoms, particularly with an acute presentation, include fever, leukocytosis, peritoneal signs, and a palpable pelvic or abdominal mass.

Radiologic investigation can include abdominal radiography that may show an abdominal mass with absence of the splenic shadow from the left upper quadrant. Serial abdominal radiographs may show variation in the position of the spleen over time. A barium contrast study would be expected to show only non-specific mass effect related to the abdominal mass. Nuclear scintigraphy would demonstrate either no splenic tracer uptake or an ectopic splenic position. Both CT and sonography would be expected to show an abdominal mass or ectopic position of the spleen, and no spleen in the left upper quadrant. Sonography demonstrates a large spleen with an inhomogenous echo texture. A CT scan with use of intravenous contrast can demonstrate lack of, or only limited enhancement of the spleen due to vascular torsion. The infarcted spleen has a CT attenuation below that of the normal spleen. Ascites also may be demonstrated by cross-sectional imaging methods. Additionally, the pancreatic tail may be torsed and infarcted. Chronic or intermittent splenic torsion may produce a chronic inflammatory enhancing splenic pseudocapsule related to development of omental and peritoneal adhesions. Finally, a "whorl" of fat and possibly pancreatic tissue may be present along the medial aspect of the spleen due to rotation of the vascular pedicle. Duplex Doppler and color flow sonography can assess the vascular flow to the spleen in cases of suspected infarction.

In the cases demonstrated here, figure 1 shows the absence of a spleen in the expected location, with the stomach, bowel, and left lobe of liver in the left upper quadrant. Figure 2 demonstrates the "whorl" sign of perivascular fat surrounding an enhancing splenic artery. The spleen is not visualized anterior to the kidney. Figures 3 and 4 show a large heterogeneous mass with patchy parenchymal enhancement in the left lateral mid abdomen producing mass effect on adjacent bowel compatible with an infarcted spleen. The pancreatic tail and surrounding fat are normal.

Other diagnostic considerations should include abdominal abscess, mesenteric or omental cyst, or mesenteric neoplasm. The lack of a spleen in the expected location strongly suggests the appropriate diagnosis. Splenectomy is required to manage the infarcted spleen, while splenoplexy can be used to treat chronic or intermittent symptoms related to splenic migration or torsion.

References

1. Herman TE, Siegel MJ: CT of acute splenic torsion in children with wandering spleen. AJR 156:151-153, 1991.

2. Nemcek AA, Miller FH, Fitzgerald SW: Acute torsion of a wandering spleen: Diagnosis by CT and duplex Doppler and color flow sonography. AJR 157:307-309, 1991.

3. Sheflin JR, Lee CM, Kretchmar KA: Torsion of wandering spleen and distal pancreas. AJR 142:100-104, 1984.