Radiology quiz

ELLEN C. BENYA, MD

aSpring 1999

A PREVIOUSLY HEALTHY  eleven-month-old boy was brought to the Emergency Department with a 48-hour history of emesis, irritability, increasing abdominal distention, and blood-tinged stools. There was no prior history of abdominal symptoms or surgery. Plain films were obtained (Figure 1).

FIGURE 1. Supine plain abdominal radiograph reveals a distal small bowel obstruction with multiple markedly dilated small bowel loops and a paucity of colonic and rectal gas.

Question: What are the plain film findings?

Findings: Supine abdominal radiograph reveals multiple markedly dilated small bowel loops with a paucity of colonic gas. There is no calcification or free intraperitoneal air detected.

Question: What is your diagnosis?

An ultrasound was subsequently performed revealing a rounded soft tissue mass with a hypoechoic rim and hyperechoic center in the right mid-abdomen (Figure 2).

FIGURE 2. Transverse ultrasound image shows a soft tissue mass (arrows) medial to the right kidney (K) and liver (L) with a hypoechoic peripheral rim and a hyperechoic center. This appearance is characteristic for an intussusception.

Question: What procedure, if any, should be performed?

Radiologic findings (continued): Contrast enema (performed with diluted Gastrografin contrast material) confirmed the presence of an intussusception which was incompletely reduced to the terminal ileum (Figure 3). At surgery the intussusception was manually reduced.

FIGURE 3. (a) Contrast enema demonstrates a filling defect in the transvers colon compatible with an intussusception (arrows). (b) Prone image at the end of the procedure reveals contrast filling of the cecum (C, below) and a small amount of reflux into the terminal ileum, however, a filling defect (arrows) due to persistent intussusception prevents normal reflux into distal small bowel.

Diagnosis: Ileoileocolic intussusception.

DISCUSSION

Intussusception is one of the acute abdominal emergencies occurring in children. In children three months to three years of age without prior abdominal surgery, intussusception is the most common cause of an acquired intestinal obstruction. It is believed that enlarged intramural lymphoid tissue (Peyer patches) in the small bowel may act as a lead point for the development of an idiopathic intussusception with invagination of the distal small bowel into the cecum and colon. Other structural lesions such as a Meckel’s diverticulum, duplication cyst, polyp or lymphoma may be lead points for an intussusception, however, these associated lead points are more frequently identified in children younger than three months of age, older than five years of age, or in children with multiple recurrent episodes of intussusception.

A child with intussusception typically has intermittent episodes of abdominal pain, emesis and bloody or "currant jelly" stools. However, the clinical presentation may be varied, occasionally with diarrhea, a palpable abdominal mass or lethargy with delay in treatment. Plain films may be diagnostic if a soft tissue mass in the cecum or transverse colon is identified or strongly suggestive of intussusception with a distal small bowel obstruction in a young child with no prior abdominal surgery. However, plain films are frequently unrevealing. Therefore, if intussusception is suspected, clinically further imaging evaluation is warranted.

Intussusception has a characteristic appearance on ultrasound (US) as shown in Figure 2. On transverse imaging through an intussusception a "target" or "donut" sign is seen with a peripheral rim of hypoechoic tissue and a hyperechoic center. On longitudinal imaging through the intussusception, the intussusceptum can be seen extending into the intussuscipiens. US has been shown to be a sensitive method for the detection of intussusception. Studies by Verschelden et al.¹ and Bhisitkul et al.² both reported a sensitivity of 100% for US in the detection of intussusception in a total of 145 children. Specificity values were 88% and 93% respectively. Bhisitkul and colleagues determined that if children with suspected intussusception were divided into two groups based on the presence or absence of the classic triad of colicky abdominal pain, vomiting, and bloody stools, a single diagnostic test could have been performed in 89% of cases. They recommended an immediate contrast enema in children with a high clinical suspicion and a screening ultrasound in those with a low clinical suspicion. Using that proposed algorithm, the child described here would have undergone immediate enema for diagnosis and attempted treatment. An additional role for US has been proposed by Lim et al.,³ who suggest that color doppler sonography can be used to assess blood flow in the intussusceptum to determine the viability of the bowel.

Contrast enemas are now an accepted form of non-surgical treatment for intussusception with success rates of 63 to 81%.^4,5 There is controversy regarding which material—barium, water-soluble contrast, or air—is best suited for intussusception reduction. Regardless of which material is used, there are several absolute contraindications to attempted enema reduction, including free intraperitoneal air on radiographs, peritoneal signs on physical examination, and significant hypovolemia, all of which suggest necrotic bowel requiring surgical treatment. While a radiographic pattern of a distal small bowel obstruction as in this case (Figure 1) is not a contraindication for enema reduction, the success rate for non-surgical reduction in these cases is significantly reduced.

REFERENCES

1. Verschelden P, Filiatrault D, Garel L, et al: Intussusception in children: Reliability of US in Diagnosis—A Prospective Study. Radiology 1992, 184:741–744.

2. Bhisitkul DM, Listernick R, Shkolnik A, et al: Clinical application of ultrasonography in the diagnosis of intussusception. J Pediatr 1992; 121: 182–186.

3. Lim HR, Bae SH, Lee KH, et al: Assessment of reducibility of ileocolic intussusception in children: Usefulness of color Doppler sonography. Radiology 1994; 191:781–785.

4. Stein M, Alton DJ, Daneman A: Pneumatic reduction of intussusception: Five-year experience. Radiology 1992; 183:681–684.

5. Meyer J, Dangman BC, Buonomo C, Berlin JA: Air and liquid contrast agents in the management of intussusception: A controlled, randomized trial. Radiology 1993; 188:507–511.

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