Swipe to advance

14 Potentially Misleading Mimics of Appendicitis

Caroline Taylor, MD | March 28, 2022 | Contributor Information

As many as 42% of patients with clinically suspected appendicitis have an alternative diagnosis that is identified on computed tomography (CT).[1] In particular, appendicitis and nephrolithiasis may be confused clinically.

In a 30-year-old man who presented with fever and right lower quadrant (RLQ) pain, the CT image shows a normal appendix (blue arrow) with a dilated right ureter (yellow arrow). Inferiorly, an obstructing calculus is visible at the right ureterovesicular junction (red arrow). Because many CT scans for the assessment of renal stones are performed without contrast, assessment of the appendix may be compromised. If no renal stones are found on a noncontrast CT, additional CT images with oral and intravenous (IV) contrast agents may be needed.[2,3]

14 Potentially Misleading Mimics of Appendicitis

Caroline Taylor, MD | March 28, 2022 | Contributor Information

There are many potential mimics of appendicitis that can be diagnosed during the imaging workup. This coronal reformatted CT scan is from a middle-aged man who presented with fever and a suppurating groin abscess. A strangulated appendix is visible within the femoral canal (arrow). The frequency of herniation of the appendix into a femoral hernia sac is below 1%; this event accounts for 0.13% of all cases of acute appendicitis.[4] Femoral hernias are thought to be due to a congenital defect; they occur more frequently in females. Because of the narrowness and rigidity of the femoral canal, the rate of incarceration is significantly higher in femoral hernias (14-56%) than in inguinal hernias (6-10%); therefore, early surgical repair is indicated.

14 Potentially Misleading Mimics of Appendicitis

Caroline Taylor, MD | March 28, 2022 | Contributor Information

This circumscribed lesion of fat density with surrounding edema (arrow) is consistent with epiploic appendagitis rather than with appendicitis.[5] Epiploic appendages are peritoneal pouches that arise from the serosal surface of the colon and are attached by a vascular stalk; they are not usually visible on CT unless inflamed.[6] These appendages are frequently associated with colonic diverticula and consist of adipose tissue and blood vessels, ranging in size from 0.5 cm to 5 cm. Epiploic appendagitis is usually a self-limiting condition and typically resolves within 10 days following treatment with oral anti-inflammatory medications.

14 Potentially Misleading Mimics of Appendicitis

Caroline Taylor, MD | March 28, 2022 | Contributor Information

Patients with chronic medical conditions may be exposed to many CT scans over their lifetime and may be exposed to larger cumulative doses of radiation.[7] Imaging must be performed judiciously based on the pretest probability of disease, and low-dose CT may be an option.[8]

This young woman presented with acute RLQ pain and fever. The appendix was normal (yellow arrow). Chronic changes related to Crohn disease were noted, including thickening of the wall of the terminal ileum (red arrow) and sacroiliitis.

14 Potentially Misleading Mimics of Appendicitis

Caroline Taylor, MD | March 28, 2022 | Contributor Information

Intra-abdominal fluid may derive from many inflammatory processes, including gallbladder disease, pyelonephritis, renal obstruction, pancreatitis, and diverticulitis. Careful evaluation of each organ is necessary, but identifying the appendix may be challenging owing to the surrounding inflammation and fluid.

This patient presented with RLQ pain. The CT image shows that fluid had tracked down the right paracolic gutter (yellow arrow) in addition to the anterior pararenal space (red arrow). The patient was diagnosed with severe acute pancreatitis with peripancreatic effusions.

14 Potentially Misleading Mimics of Appendicitis

Caroline Taylor, MD | March 28, 2022 | Contributor Information

Even though appendicitis is often the most likely diagnosis in patients with RLQ pain, a high index of suspicion must be maintained. Depending on the age, clinical presentation, and other medical conditions, the differential diagnosis list includes diverticulitis of the right colon or redundant sigmoid, inflammatory or infectious colitis, perforated carcinoma, and ischemia.

This 81-year-old man presented with RLQ pain. CT shows extensive colonic diverticulosis with diverticulitis of the sigmoid colon. Mesenteric infiltration (yellow arrow) and an adjacent normal-appearing appendix (blue arrow) are shown.

14 Potentially Misleading Mimics of Appendicitis

Caroline Taylor, MD | March 28, 2022 | Contributor Information

This 63-year-old man with an inguinal hernia was incidentally found to have an appendiceal mucocele. The CT image shows internal calcifications (arrow) and extension into the inguinal canal through a patent processus vaginalis.

Acute appendicitis can occur in association with a mucocele. Cystic dilatation of the appendix, mural calcification, and a luminal diameter greater than 1.3 cm are alerting findings.[9] Correct identification is important because spillage of fluid at surgery may result in pseudomyxoma peritonei, and more extensive surgical resection may be warranted for malignant mucoceles.[10]

14 Potentially Misleading Mimics of Appendicitis

Caroline Taylor, MD | March 28, 2022 | Contributor Information

A 59-year-old patient with known hepatocellular carcinoma presented with midabdominal and RLQ pain. Imaging shows mesenteric infiltration and small bowel wall thickening in the RLQ (blue arrow). The appendix was found to be normal, and a large thrombus was identified in the main portal vein (yellow arrow). The use of IV contrast allowed assessment of the arterial and venous systems of the abdomen. The patient's abdominal pain was caused by mesenteric vein congestion and increased portal venous pressures. Portal vein thrombosis is a recognized risk associated with chronic hepatic disease.

14 Potentially Misleading Mimics of Appendicitis

Caroline Taylor, MD | March 28, 2022 | Contributor Information

The CT image for this woman, who presented with abdominal pain, reveals a normal retrocecal appendix (blue arrow). However, lower-pole inflammatory changes in the right kidney are consistent with pyelonephritis (yellow arrow). For pregnant women and pediatric patients, ultrasonography (US) and magnetic resonance imaging are the recommended imaging modalities because of concerns regarding radiation exposure. Radiation exposure for CT of the abdomen and pelvis can be in the range of 5-20 mSv for a single examination.[11]

14 Potentially Misleading Mimics of Appendicitis

Caroline Taylor, MD | March 28, 2022 | Contributor Information

This young woman presented with abdominal pain and was found to have a hemorrhagic ovarian cyst with hemoperitoneum (arrow), confirmed via laparoscopy. Women are more likely than men to have an alternative diagnosis for RLQ pain. Numerous gynecologic conditions may present as RLQ pain, including salpingitis, ovarian torsion, ruptured dermoid cyst, and ruptured ectopic pregnancy.[12] If abdominal CT does not identify a definite cause, transvaginal US (TVUS) may be helpful in elucidating gynecologic conditions that are not well delineated on CT.

14 Potentially Misleading Mimics of Appendicitis

Caroline Taylor, MD | March 28, 2022 | Contributor Information

This 28-year-old woman presented with 7 days of RLQ pain. She had been on birth control for 15 years but stopped several months before presentation. For the past few months, she had been experiencing painful periods and RLQ pain. A focal cystic structure with focal higher attenuation elements can be seen in the midabdomen (red arrow). The appendix is normal (blue arrow). Subsequent TVUS was performed and revealed a complex cystic structure in the right ovary, with peripheral increased vascular flow consistent with a hemorrhagic corpus luteal cyst. Repeat US after two menstrual periods was recommended.

14 Potentially Misleading Mimics of Appendicitis

Caroline Taylor, MD | March 28, 2022 | Contributor Information

This elderly man presented with RLQ pain and guarding. The CT image shows active extravasation of contrast material (arrow) from a ruptured abdominal aortic aneurysm. In elderly patients, the likelihood of vascular disease is dramatically increased. Patients with other conditions that involve the right psoas may present with RLQ pain.

14 Potentially Misleading Mimics of Appendicitis

Caroline Taylor, MD | March 28, 2022 | Contributor Information

An elderly man presented with fever, RLQ pain, and an elevated WBC count. As shown on this CT image, the patient had a normal retrocecal appendix, but the terminal ileum was markedly thickened (arrow), and lymph nodes 1-1.5 cm in size were present at the root of the mesentery (not shown). During surgery, a carcinoid tumor of the ileum was found, with serosal involvement causing ischemia. Note the nodular, irregular thickening of the terminal ileum.

14 Potentially Misleading Mimics of Appendicitis

Caroline Taylor, MD | March 28, 2022 | Contributor Information

This elderly patient presented with fever, an elevated WBC count, and crampy RLQ pain. The CT image demonstrates thickening of the cecum, with pneumatosis of the cecal wall (arrow). The appendix is normal in diameter and separate from the mesenteric stranding. During surgery, an ischemic right hemicolon was resected. The patient had a prosthetic mitral valve, and the ischemia was thought to represent an embolic phenomenon.

1 26 Next
References