Rare Childhood Bowel Condition Hid From Ultrasound Until a Subtle CT Clue Emerged

Intussusception, the condition in which one segment of the intestine slides inside another like a collapsing telescope, is one of the most common causes of an acute abdomen in young children. Pediatricians and emergency physicians are trained to look for its classic ultrasonographic signature, the so-called target sign, a concentric ring pattern that has been described since 1985 and that gives ultrasound a reported sensitivity of roughly 95 percent. Yet a newly published case report in Clinical Case Reports describes a four-month-old boy in whom that familiar sign was entirely absent, and in whom the true diagnosis only became clear through a subtle finding on contrast-enhanced computed tomography that the treating team recognized only in retrospect. The case, which the authors describe as the first report of its kind, offers a vivid lesson in how a rare anatomical variant of a common disease can defeat even the most trusted diagnostic tools.

The infant’s story began with vomiting that his parents could not ignore. There was no diarrhea, and nothing in the early course suggested simple enteritis. What alarmed clinicians at the first hospital was the character of the vomit: it was green and bile-like, a warning that something might be obstructing the bowel downstream of the stomach and duodenum. On arrival, the boy’s vital signs were relatively reassuring. His temperature was 37.4 degrees Celsius, his pulse 124 beats per minute, his blood pressure 79 over 48 millimeters of mercury, and his respiratory rate 41 breaths per minute. His peripheral oxygen saturation was a perfect 100 percent on room air. But the physical examination told a more troubling story. His vitality was slightly decreased, his abdomen was distended, and his bowel sounds were diminished.

Curiously, despite what would turn out to be dying bowel inside his abdomen, the infant showed almost no signs of peritoneal irritation, the rebound tenderness and guarding that usually accompany a surgical emergency of this kind. That absence would later prove to be one of the most instructive features of the case. What the boy did have was massive hematochezia, the passage of bloody stool, which is a clinical finding that strongly suggests bowel necrosis. Laboratory tests revealed early-stage inflammation, with a white blood cell count of 15,900 per microliter and a C-reactive protein level of 3.84 milligrams per deciliter, along with slight anemia at a hemoglobin of 12.4 grams per deciliter. Arterial blood gas analysis showed a pH of 7.48 with a bicarbonate level of 19.3 millimoles per liter, a base excess of minus 2.6, and a lactate of 1.0, a pattern consistent with compensated metabolic acidosis.

Abdominal radiography demonstrated findings consistent with ileus, the failure of the bowel to propel its contents, prompting the team to perform contrast-enhanced computed tomography. That scan revealed a closed-loop configuration, and based on a diagnosis of strangulated ileus, the infant was emergently transferred to the authors’ hospital. Only later, and then retrospectively, did reviewers recognize that the CT images had actually shown a bowel-within-bowel appearance that had not been appreciated preoperatively. More importantly, the images displayed a characteristic double-enhanced layer: an inner layer representing necrotic intestine, and an outer layer corresponding to viable colon with preserved blood flow, with fluid accumulation noted between them. The inner layer appeared discontinuous, and frond-like loops of small bowel were visible, resembling a multipolypoid mass.

Ultrasonography, the first-line diagnostic modality in children with suspected intussusception, had failed to show the classic target or doughnut signs. Instead, color Doppler imaging identified only an absence of blood flow within the intestinal wall, a finding that in retrospect resulted from hemorrhagic and necrotic tissue. The authors explain the missing target sign through three pathological mechanisms: necrosis and thickening of the incarcerated bowel, necrosis and dissolution of the mesenteric fat and vessels, and distortion of the bowel configuration caused by the necrotic mesentery. When the normal layered anatomy of the intussusceptum is destroyed in this way, the concentric rings that radiologists rely on simply cease to exist, and the examination that is usually near-definitive becomes misleadingly normal or nonspecific.

The differential diagnosis at the time included internal hernia and strangulated ileus caused by a Meckel’s band. The team also considered a vaccine-related cause. In Japan, the rotavirus vaccine is administered within 14 weeks of birth, and this patient had received it; however, more than a month had passed since vaccination, making a side effect unlikely. With no definitive diagnosis established, the decision was made to proceed with emergency surgery. A nasogastric tube was not inserted before transfer because the child went straight to the operating room, and by the time the tube was placed he had already vomited a small amount of contents. What followed was an operation that tested the surgeons’ ability to read anatomy that had been turned inside out.

Upon opening the abdomen, the surgical team could not immediately identify necrotic bowel, precisely because the dead segment was hidden inside living tissue. Only careful palpation revealed a firm mass within the colon, at which point an intraluminal colonic lesion was suspected for the first time and a colotomy was performed. Necrotic bowel was indeed found within the colonic lumen, confirming the diagnosis of intussusception. Manual reduction using Hutchinson’s maneuver was unsuccessful, so the surgeons resected a 30-centimeter section of small intestine including the necrotic portion. The colon was spared, and the ileocecal valve was preserved. A double-barrel ileostomy was created, with the anal-side small bowel brought out as a mucous fistula. Two months later the stoma was closed, and at one-year follow-up the boy was tolerating oral feeding, growing appropriately, and free of recurrence, with abdominal radiography showing no evidence of obstruction.

Examination of the resected specimen settled the anatomical question: the ileum had invaginated into the colon, confirming an ileoileocolic-type intussusception, with the mesenteric vessels and fat within the invaginated segment completely necrotic and liquefied. This subtype is the crux of the case. The most common form of intussusception in children is the ileocolic type, which can usually be diagnosed easily on ultrasound. The ileoileocolic type is rare, harder to diagnose, and associated with a significantly higher incidence of bowel necrosis. Its success rate for nonoperative reduction is only about 10 percent, which is why the authors argue that it should be diagnosed promptly and treated with surgical intervention rather than reduction by high-pressure enema. In this subtype, the necrotic segment sits within normal bowel, which is exactly why identifying the dead tissue was so time-consuming in the operating room; anticipating it preoperatively, the authors note, would have shortened the operation and reduced the burden on the patient.

The case also resolves a physiological puzzle: why a child with necrotic bowel lacked peritoneal signs. The authors suggest that in intussusception, exudate from the necrotic segment is released into the colonic lumen rather than into the peritoneal cavity, blunting the inflammatory irritation of the abdominal lining that usually signals disaster. Meanwhile, more than 90 percent of childhood intussusception cases are idiopathic, with roughly 5 percent attributable to a pathological lead point such as lymphoid hyperplasia, Meckel’s diverticulum, duplication cysts, intestinal polyps, mesenteric lymphadenopathy, lymphoma, prior surgery, or trauma. In this infant, no cause could be determined, and the small number of reported ileoileocolic cases precludes identifying any region-specific pattern.

Perhaps the most consequential imaging lesson concerns the double-enhanced layer itself. On contrast-enhanced CT, the bowel wall presumed to be necrotic exhibited hyperattenuation and looked deceptively similar to viable bowel, an appearance the authors attribute to capillary hemorrhage originating from the necrotic bowel wall. The team initially interpreted the inner wall as living tissue; it was in fact necrotic mucosa stained by hemorrhage. Misreading this hyperattenuating inner layer as viable intestine could lead clinicians to underestimate the extent of bowel death and delay surgery, with potentially catastrophic consequences. Prior reports had described a multipolypoid appearance on contrast enema and frond-like loops on ultrasonography in this condition, but the authors believe this is the first description of a double-enhanced layer on contrast-enhanced CT in ileoileocolic intussusception mimicking viable bowel. For emergency physicians, radiologists, and pediatric surgeons, the message is stark: when the target sign is missing but a child is sick, the absence of a classic finding may itself be the finding, and the brightest layer on the scan may be the deadest bowel in the abdomen.

Subject of Research: Ileoileocolic intussusception with atypical imaging findings in a pediatric patient

Article Title: Ileoileocolic Type Intussusception With Double Enhanced Layer Sign in a Pediatric Patient: A Case Report

Article References: Sakamoto, N., Take, Y., Nemoto, Y., Ono, K., Tanaka, Y., & Masumoto, K. (2026). Ileoileocolic Type Intussusception With Double Enhanced Layer Sign in a Pediatric Patient: A Case Report. Clinical Case Reports, 14(10), Article e73707. https://doi.org/10.1002/ccr3.73707

Image Credits: AI Generated

DOI: 10.1002/ccr3.73707

Keywords: intussusception, pediatrics, ileoileocolic, contrast-enhanced CT, target sign, bowel necrosis, ultrasonography, emergency surgery, strangulated ileus, case report, double enhanced layer sign, ileostomy