A 25-year-old male presented in ER with RLQ pain, burning micturition, vomiting and fever for the past 3 days. On examination, patient had temperature of 98.6 F, pulse and respiratory rate of 82 and 18 per minute respectively with BP of 125/87 mmHg. All haematological parameters were within normal range except WBC count of 17,400. On physical examination, the abdomen was tender on palpation specifically in the RLQ.
Initially, CT FACT was planned, which showed prominence of distal ileal segment, approximately 34 mm, containing fluid and high attenuation material within the lumen. There was also surrounding fat stranding however, the bowel loops proximal to it appeared non-distended. (Figure 1) The appendix appeared normal with luminal diameter of 6 mm without any signs of inflammation to suggest appendicitis. (Figure 2)
CT abdomen with oral contrast was then recommended which revealed a thick-walled blind ending tubular structure arising from the distal ileal loop in the right iliac fossa, mimicking appendix, measuring approximately 50 x 32 mm. There was associated surrounding fat stranding without any contrast material within its lumen. (Figure 3) Multiple prominent enlarged non-enhancing mesenteric lymph nodes were also identified, the size of the largest measured 8 mm in the short axis. (Figure 4)
No abscess, free fluid or bowel obstruction could be seen. The appendix was located anterior to the caecum appearing normal. It was concluded as Acute Meckel Diverticulitis with normal appendix.
Regardless of advanced imaging modalities, Meckel's diverticulitis (MD) is still difficult to diagnose pre-operatively. Most of the cases are being misdiagnosed as acute appendicitis, which is more common in older patients and according to the literature it accounts for 12.7-53.3% of all the symptomatic cases . In the absence of bleeding, a preoperative diagnosis of symptomatic MD is difficult in the adult population. Fewer than 10% of symptomatic MD cases are diagnosed prior to the surgery .
It has been proposed in prior research that search for an MD should be routine and also an emphasis has been given on careful exploration of surrounding organs even though appendicitis has been diagnosed.
MD is a true diverticulum containing all of the layers of a normal small bowel and is usually located along the antimesenteric border of ileum about 50 to 100 cm from the ileocaecal valve . It is a common congenital gastrointestinal tract anomaly resulting from incomplete obliteration of the vitelline duct and accounts for 90% of all vitelline duct anomalies . MD is commonly asymptomatic, with symptoms usually due to the presence of a complication. It is more common in males and classically presents before 2 years of age . Bleeding is the most common presentation in children while intestinal obstruction is most common finding in adults . It becomes inflamed as a result of obstruction at the base of the diverticulum.
Despite advances in imaging techniques, the diagnosis of symptomatic MD is still difficult with most cases preoperatively being diagnosed as acute appendicitis . The modality of choice is Technetium-99m pertechnetate scintigraphy, with sensitivity and specificity as high as 90%-95% [1,2]. However, it is less sensitive (63%), specific (2%), and accurate (46%) in the adult patients since the prevalence of heterotopic gastric mucosa declines as the age progresses in symptomatic Meckel's diverticulum. Therefore it is rarely used for evaluation of acute abdomen unless there is high clinical suspicion. 
Plain films and fluoroscopic studies only show complications of MD such as bowel obstruction or perforation while ultrasonography demonstrates only peritoneal fluid in the majority of the cases and rarely can it show inflamed diverticulum, which is difficult to distinguish from inflamed appendix. CT is believed to be the most sensitive cross-sectional modality for diagnosing complicated MD, in cases where normal appendix is visualized. [7, 8]
As demonstrated in our case misdiagnosis can occur even on CT scan if Meckel diverticulitis or perforation is secondarily complicated by appendicitis. Key finding is an intact appendix in the setting of a collection that has a communication with the ileum. Therefore a careful review of the images is warranted especially when the inflamed appendix appears intact as was in our case.
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