Right Iliac Fossa Pain other than Appendicitis: A Pictorial Review

Right-sided rectus sheath hematomas typically occur in anticoagulated patients and cause focal tenderness. They appear as lens-shaped mass in the anterior abdominal wall, contained by the rectus sheath and may be anechoic, show heterogeneous echogenicity, or a fluid–fluid level [ Figure 10 ].[ 23 ] Rectus sheath Hematoma: Two anticoagulated patients, both showing a large hematoma in the abdominal wall. (a) A fluid–fluid level while (b) A heterogeneous echogenic mass

Epiploic appendagitis is due to the infarction of an epiploic appendage, usually due to torsion or thrombosis of its feeding vessels. Ultrasound shows a tender, hyperechoic, avascular, ovoid mass surrounded by a hypoechoic rim that is typically 2–4 cm and attached to the parietal peritoneum [ Figure 6 ].[ 18 ] As thrombosis of the feeding vessels may be secondary to the inflammation of nearby structures, careful examination for other pathologies should be performed. Epiploic Appendagitis: An ovoid, echogenic mass with a hypoechoic rim was seen adjacent to the peritoneum at the site of maximal tenderness. No other abnormality was found

Intussusception is classically seen in young children, who may or may not be able to localize their pain when the ileum invaginates into the colon (ileocolic intussusception). It is the most common cause of small-bowel obstruction in children. Ultrasound shows a thickened, multilayered appearance of bowel within bowel, described as an “onion” or “target” sign when viewed in transverse orientation. Centrally, there will be a crescentic hyperechoic region due to invaginated mesentry [ Figure 4 and Video 3 ].[ 13 14 ] There is increasing recognition of short segment, brief, transient, self-resolving ileoileal intussusception without an identified lead point, which may be incidental or occur in association with many other conditions (due to hyperperistalsis, lymphoid hyperplasia, focal wall thickening, etc.). As this type of intussusception is self-resolving, it does not have the same treatment implications as either persisting intussusception or ileocolic intussusception.[ 8 15 16 ] Intussusception: The “target” or “onion” appearance of bowel within bowel seen in intussusception

Multiple enlarged (>8 mm in short axis of at least one) lymph nodes may be due to presumed viral infection and are a common cause of right iliac fossa pain in children [ Figure 5 and Video 4 ].[ 17 ] However, reactive lymph nodes can occur in association with many conditions (including appendicitis), so careful examination to exclude other pathologies should be performed before concluding the pain is due to mesenteric adenitis. Mesenteric Adenitis: Multiple lymph nodes are seen in the right iliac fossa (arrows). A normal appendix was also visualized and no other abnormality seen

Ovarian pathologies, such as hemorrhagic cysts, cyst rupture, and torsion, may all present as right iliac fossa pain in female patients, although usually with a more rapid onset of pain. Ovarian torsion, in particular, can be a difficult clinical and sonographic diagnosis with varied clinical presentation (vomiting is reported between 30% and 80% and pain levels can fluctuate). Sonographic features are classically an enlarged, edematous ovary with prominent follicles due to hyperechoic rims [ Figure 9 and Video 5 ], and a focal ovarian mass (e.g., cyst). The ovary may be in an abnormal position. A “whirlpool sign” of the twisted pedicle has high specificity but poor sensitivity. It should be remembered that the presence of color Doppler flow is seen in half of (surgically proven) ovarian torsion cases, and spectral Doppler may reveal both arterial and venous flow.[ 20 21 22 ] Ovarian torsion: An enlarged (141 mL), edematous ovary with prominent peripheral follicles is seen. No ovarian mass was seen, and color Doppler flow was present (not shown). Surgery confirmed ovarian torsion

Psoas abscesses can occur from primary hematogenous seeding or secondary to spread from adjacent infection. If right sided, it can cause right iliac fossa pain and tenderness, classically associated with hip pain. Ultrasound demonstrates a heterogeneous mass within the psoas muscle with a loss of the normal muscle striation [Figure 11a and b ].[ 24 ] Psoas Abscesses: Both images show a heterogeneous collection within the psoas with a loss of the normal striated muscle pattern. (a) Is a right psoas abscess from Staphylococcus, (b) is a left psoas abscess due to tuberculosis

Although the clinical presentation of renal colic is typically different (flank pain and microscopic hematuria), a distal ureteric stone may present as right iliac fossa pain. Ultrasound generally shows hydronephrosis and an echogenic, shadowing stone may be seen in the ureter [ Figure 7 ].[ 19 ] Renal Colic: An echogenic, shadowing mass is seen in the dilated distal ureter. Hydronephrosis of the right kidney was also present (not shown) Similarly, the clinical presentation of pyelonephritis is usually evident; however, it should be remembered that appendicitis may occasionally cause leukocytes in the urine (especially if the inflamed appendix is lying adjacent to the bladder).[ 3 ] Ultrasound in pyelonephritis is generally normal but may show either hypoechoic or hyperechoic segmental areas and an area of reduced color Doppler flow [ Figure 8 ]. Ultrasound can also be useful to detect hydronephrosis or abscess formation.[ 19 ] Pyelonephritis: The upper pole of the kidney contained a wedge-shaped echogenic region. Urine examination was consistent with pyelonephritis

Terminal ileitis can be due to infectious causes and Crohn's disease. Thickened bowel (>3 mm) may be seen in both causes. Crohn's disease may also show loss of the bowel wall layers, creeping fat, strictures, and other complications of inflammatory bowel disease,[ 8 ] but ultrasound may not be able to distinguish between infectious and inflammatory bowel disease. In susceptible patients, tuberculosis can also cause terminal ileitis[ 9 ] [ Figure 2 ]. Crohn's Disease: Markedly thickened and hyperemic terminal ileum with a loss of the bowel wall layers was seen in a patient referred for “grumbling appendix.” Crohn's disease was confirmed on subsequent colonoscopy

Right iliac fossa pain is a common presentation to the emergency department.[ 1 2 ] Although appendicitis is the most common surgical emergency,[ 3 ] there are many other causes of right iliac fossa pain that must be considered when evaluating these patients [ Table 1 ].[ 1 2 3 ] Ultrasound is frequently recommended as the primary imaging modality for the investigation of acute abdominal pain, especially in young patients,[ 4 5 6 ] and can often demonstrate the cause of the pain in these patients. This article will describe some of the pathologies, other than appendicitis, that can present as right iliac fossa pain, and that may be seen when scanning a patient for “query appendicitis.” Causes of right iliac fossa pain

Appendicitis is a common cause of right iliac fossa pain, but there are many other causes that must be considered. While the history and clinical examination will generally guide the differential diagnosis, there is often overlap of the findings, so ultrasound can be extremely useful in these patients. In particular, if ultrasound demonstrates a normal appendix, or the appendix is not seen, then other causes should be considered and specifically examined for. Nil. There are no conflicts of interest.