A rare presentation of acute appendicitis

A previously healthy 32-year-old man presented with 2 days abdominal pain, located in RUQ. He had fever and nausea, and denied vomiting and diarrhoea. Vital signs showed fever and tachycardia. Physical examination revealed tenderness in the RUQ, without abdominal rigidity. Laboratory analysis showed neutrophilia, and elevated CRP and total bilirubin.

With this medical history suggestive of acute cholecystitis, abdominal ultrasound was performed. It showed a gallbladder with normal thin wall, without any sludge or stone. But it showed a hypoechoic, bowel-like structure in the RUQ, with 10 mm transverse diameter, which was surrounded by hyperechoic fat tissue.

Abdominal CT-scan with contrast was additionally performed. It revealed a blind-ended bowel loop in the RUQ with luminal distention and wall thickening, compatible with an inflamed appendix. It was surrounded by hyperattenuating fat due to oedema and inflammation. It contained a 15 mm-sized calcified deposit within its lumen, indicating an appendicolith. The CT also showed wall thickening in the adjacent caecum and in the right colic flexure due to direct extension of the local inflammatory process. Furthermore there were local enlarged lymph nodes, and pelvic free fluid. There was no periappendiceal abscess.

Acute appendicitis is the most common surgical emergency and one of the most common causes of acute abdominal operations worldwide [2, 8].
Acute appendicitis typically presents with acute RLQ abdominal pain, anorexia, nausea and vomiting. McBurney's point tenderness is the most sensitive sign on physical examination (50-94% sensitivity) and has 75-86% specificity [8].
There are different anatomic variations in the localisation of the appendix. The most common location of the appendix is retrocaecal (60-65%). Other documented sites are pelvic (30%), retroperitoneal (7%), subcaecal (2, 3%), and preileal (1%) [6, 7].
Subhepatic appendix is a very rare phenomenon and is only reported in 0.08% of all appendicitis, which equals to an incidence of 0.09 per 100,000 population annually [2]. It occurs because of an anomaly during fetal development of the midgut, in which caudal migration of the caecum towards the right iliac fossa fails, resulting in subhepatical position of the caecum and appendix [1, 5].
Patients with subhepatically located caecum and appendix may present with atypical signs and symptoms of acute appendicitis, because the appendix is high-positioned [3]. Such patients typically present with RUQ pain, and may also have RUQ abdominal tenderness on physical examination, which mimics hepatobiliary or gastric pathologies [2].
The most important differential diagnoses of subhepatic appendicitis are acute cholecystitis and hepatic abscess [2].
The unusual clinical presentation of subhepatic appendicitis may cause delay in proper diagnosis and increases risk of complications such as suppuration, perforation and subsequent morbidities [2].
Clinical suspicion and proper diagnostic imaging are important to making the correct diagnosis and initiating relevant treatment to reduce the risk of complications.
Ultrasound is a non-expensive, available and easy-to-perform imaging method, which is the preferred first-line screening tool to diagnosis of patients with RUQ abdominal pain. Nevertheless, a subhepatic pathology may be misdiagnosed as cholecystitis or liver abscess. Presence of faecolith could be also mistaken for gallstone on ultrasound [1, 2, 4].
Computed tomography is less accessible and poses the risk of radiation, but it provides high sensitivity (100%), specifity (95%), and accuracy (98%) in diagnosing acute appendicitis, and is very useful to exclude the other abdominal pathologies [2].
Surgeons as well as radiologists should be aware of unusual locations of the appendix, which causes unusual presentation of acute appendicitis, suggestive of other causes of abdominal pain [1, 3].

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