Child’s suspected appendicitis reveals rare absence of the appendix

A 3-year-old boy admitted with 38 hours of abdominal pain, fever and bilious vomiting was found during surgery to have no appendix, according to a 2026 case report in Frontiers in Pediatrics. The child underwent surgery because his symptoms, physical examination and laboratory tests strongly suggested acute appendicitis with localized peritonitis. Yet a systematic laparoscopic and open examination of the ileocecal region found neither an appendix nor appendiceal remnant, leading surgeons to diagnose Collins Type III appendiceal agenesis, a rare congenital condition in which the appendix is entirely absent but the caecum appears normal.

The boy was 3 years and 1 month old and had been healthy before admission. His intermittent abdominal pain had begun 38 hours earlier, with intermittent fever reaching 38.0 °C and seven to eight episodes of non-projectile, bilious vomiting. During the 10 hours before presentation, the pain intensified and shifted to the right side of the abdomen. He had not passed stool and denied diarrhoea or dysuria. He had no previous abdominal operation, trauma or transfusion, and there were no visible surgical scars. The absence of previous surgery was important because it excluded appendectomy as an explanation for the missing organ.

Examination showed moderate abdominal distension, marked right-sided tenderness, guarding and rebound tenderness. Bowel sounds were reduced to one or two per minute. Blood tests revealed leukocytosis with neutrophil predominance: the white blood cell count was 12.9 × 10⁹/L and the neutrophil count was 9.82 × 10⁹/L. C-reactive protein was elevated at 45.75 mg/L, while haemoglobin and platelet values were within paediatric reference ranges. These findings supported an acute inflammatory abdominal process, although they could not identify its cause or distinguish appendiceal agenesis from appendicitis.

Abdominal-pelvic computed tomography also failed to show the appendix. Instead, it revealed pericecal exudative changes and several enlarged mesenteric lymph nodes. The preoperative clinical impression was an acute abdomen, highly suggestive of acute appendicitis with localized peritonitis. The case illustrates an important limitation of imaging in this setting: a nonvisualized appendix is not diagnostic of congenital absence. The source article notes that inflammation, a retrocaecal position and technical limitations can all prevent an appendix from being seen on CT.

During laparoscopic exploration, the caecum was located in the right mid-abdomen and was attached to the lateral abdominal wall and right iliac fossa by adhesions. Surgeons lysed these adhesions and followed the taeniae coli toward their convergence point but identified neither an appendix nor a remnant. They then opened the retrocaecal peritoneum to expose the retrocaecal space fully, again finding no appendiceal tissue. A 2.5-centimetre extension of the abdominal incision allowed the ileocaecal segment to be exteriorized for direct manual palpation of the caecal wall.

That additional examination found no intramural or intussuscepted appendix, supporting the classification of the case as Collins Type III appendiceal agenesis. The operation also included retrograde inspection of approximately 1.5 metres of distal small bowel from the ileocaecal junction, excluding a Meckel’s diverticulum and other small-bowel malformations. Markedly enlarged mesenteric lymph nodes were observed, including one measuring 2.5 × 2.5 × 3 cm. Two representative specimens, one of them from the largest node, were taken for postoperative histopathology; no intraoperative frozen-section analysis was performed.

The five-part Collins system separates caeco-appendiceal developmental abnormalities by anatomy. Type I features complete absence of both caecum and appendix; Type II has a rudimentary caecum without an appendix; Type III, the category identified in this child, has a normal-appearing caecum with no appendix; Type IV has a normal caecum with a rudimentary or hypoplastic appendix; and Type V features a markedly dilated caecum without an appendix. Type III is described in the report as the most common phenotype in the available clinical literature, while the estimated incidence of appendiceal agenesis is roughly one in 100,000 surgical explorations for suspected appendicitis.

Confirming agenesis requires more than failing to find the appendix during surgery. Surgeons must review the patient’s operative history, mobilize the caecum and ascending colon, trace the taeniae coli, inspect the retrocaecal and ileocaecal regions, palpate the caecal wall and exclude a Meckel’s diverticulum. The investigation must also consider an intramural, intussuscepted, hypoplastic or ectopic appendix, along with appendiceal atresia, in which appendiceal tissue persists despite discontinuity of its lumen from the caecum. An ectopic appendix can occur in several unusual locations, although retrocaecal and pelvic positions are more common. The report emphasizes that a standardized exploration reduces the risk of mistaking an atypical appendix for true agenesis.

The precise cause of appendiceal agenesis remains uncertain. The report describes an embryonic process in which the appendix develops from a caecal diverticulum around the eighth week of intrauterine development. Disrupted development may result in complete absence. A leading hypothesis is an intrauterine mesenteric vascular accident between the seventh and twelfth weeks of gestation, causing ischaemic injury to the developing caecal diverticulum. Proposed influences also include teratogenic exposure, such as maternal thalidomide, and spontaneous intrauterine auto-amputation following torsion or inflammation. These mechanisms remain hypotheses and cannot be established from the clinical course of an individual child.

After the anatomical finding was confirmed, surgeons evaluated other possible explanations for the child’s acute-abdomen presentation. The authors considered intra-abdominal adhesions and reactive mesenteric lymphadenopathy the most likely contributors. This mattered because appendiceal agenesis alone does not account for the pain, fever, inflammatory laboratory results and pericecal changes that prompted surgery. The child received intravenous cefoperazone-sulbactam and metronidazole for infection management, together with fluid resuscitation and supportive care. Fever subsided gradually and abdominal discomfort resolved. On postoperative day 3, he passed flatus and stool, began clear fluids and progressed to a regular diet without vomiting or distension.

The surgical incisions healed primarily, and the boy was discharged on postoperative day 6 in stable condition while the permanent lymph-node histopathology remained pending. He was followed for three months and remained asymptomatic, without recurrent abdominal pain or fever; his abdominal examination was unremarkable. The final histopathological report identified reactive lymphadenopathy with no granulomatous inflammation or neoplastic lesions. As a single case report, the study cannot establish how often this combination occurs or whether the proposed mechanisms apply to other patients. Its practical value is narrower: when an appendix cannot be located, appendiceal agenesis belongs in the differential diagnosis, but it should be declared only after a thorough surgical search and assessment for other causes of acute abdominal pain.

Subject of Research: A paediatric case of appendiceal agenesis initially presenting with symptoms resembling acute appendicitis.

Article Title: Appendiceal agenesis in a 3-year-old boy presenting with suspected acute appendicitis: a case report

Article References: Yang, X., Wang, L., Zhang, D., & Yang, X. (2026). Appendiceal agenesis in a 3-year-old boy presenting with suspected acute appendicitis: a case report. Frontiers in Pediatrics, 14, Article 2012352. https://doi.org/10.3389/fped.2026.2012352

Image Credits: AI Generated

DOI: 10.3389/fped.2026.2012352

Keywords: appendiceal agenesis, paediatric surgery, acute appendicitis, appendix, ileocecal region, laparoscopy, mesenteric lymphadenopathy, case report, congenital anomaly, Appendiceal, agenesis, year-old