Acute Abdominal Pain and Constipation in 8-Year-Old Girl

An 8-year-old girl with a medical history of well-controlled asthma and constipation is admitted to a children’s hospital following a 5-day history of abdominal pain.The patient and her family were on a summer camping trip in the Midwest when she began to complain of increasing and persistent abdominal pain localized to the right lower quadrant over the course of 5 days. The pain was not relieved with rest or ibuprofen. Because of inconsolable pain, the family presented to the nearest emergency department.Initial evaluation included a normal physical exam. Laboratory findings included a C-reactive protein (CRP) of 40 mg/L, urinalysis with white blood cell count (WBC) of 15 per high power field (hpf) and an otherwise normal comprehensive metabolic panel, complete blood count, and urinalysis. No additional inflammatory markers were obtained. Her abdominal ultrasound did not visualize the appendix, but no abnormalities were otherwise noted. She was discharged with supportive management.A total of 24 hours later, her abdominal pain increased, and the family presented to the nearest children’s hospital. Her review of systems was positive for nausea and infrequent stools. She denied diarrhea, rashes, headaches, dysuria, or fever.The physical examination was notable because it was tearful and uncomfortable, but the girl did not appear ill. She had a heart rate of 120 beats per minute, blood pressure of 117/84 mm Hg, a temperature of 37.4°C, and a respiratory rate of 20 breaths per minute. Her weight was 38.3 kg (84 lb, 7 oz) and a body mass index (BMI) of 22.6 kg/m2 (97%). Her abdomen was tender to deep palpation in the suprapubic region, with rebound tenderness and guarding in the right lower quadrant, and bowel sounds were present in all four quadrants. Her cardiovascular, pulmonary, head, eyes, ears, neck, throat, skin, neurologic, and genitourinary exams were normal.An investigation revealed an increasing CRP (62 mg/L) and a now normal urinalysis with a WBC of 1/hpf. Urine culture from the community hospital was unavailable. Complete blood count shows normal WBC with elevated neutrophils, and a comprehensive metabolic panel was overall normal (Table 1). A repeat abdominal ultrasound visualized the appendix measuring 5 to 6 mm in diameter near the tip with no surrounding inflammatory change, which was deemed normal. Additionally, a patch of inflexible and echogenic fat deep to the abdominal wall was seen, as shown in Figure 1. Given the intensity of the pain, the abnormal ultrasound, rising CRP, and concerns for potentially surgical etiologies such as intra-abdominal abscess, an abdominal computed tomography (CT) scan was obtained and revealed the diagnosis.The differential diagnoses for right lower quadrant pain in a pre-adolescent girl include inflammatory and noninflammatory conditions. Among these are appendicitis, inflammatory bowel disease, gastroenteritis, omental infarction, mesenteric contusion, epiploic appendagitis, ovarian torsion, ectopic pregnancy, nephrolithiasis, urinary tract infection, abscess, constipation, an ischemic bowel, and malignancy. With the acute onset of symptoms in our patient, appendicitis, ovarian torsion, urinary tract infection, nephrolithiasis, acute on chronic constipation, gastroenteritis, and omental infarction are most likely. Given acute presentation, premenarchal status, and no past abdominal medical or surgical history, abscess, malignancy, ectopic pregnancy, inflammatory bowel disease and ischemic bowel are less likely. Repeat urinalysis being normal was reassuring against nephrolithiasis or urinary tract infection.A contrast-enhanced abdominal CT revealed abnormal mass-like fat seen in the right lower quadrant deep to the abdominal wall with mild internal stranding and internal vascular swirling, as seen in Figures 2 and 3. Bilateral ovaries were visualized and normal in appearance. The radiologist also commented on a moderate stool burden throughout the colon. The abnormal ultrasound result and CT findings in combination with the symptomatology were consistent with omental infarction.Omental infarction is the result of the torsion of vessels supplying the greater omentum. Infarction of the greater omentum is a rare cause of acute abdominal pain in the pediatric population occurring in approximately 0.1% to 0.5% of children undergoing surgical intervention for suspected appendicitis.1 Average age of onset varies and ranges from 3 to 17 years of age, and the major risk factor for occurrence is obesity.1 Omental infarction is associated in case reports with elevated BMI, hypercoagulable states, trauma, vascular torsion, vascular congestion secondary to right heart failure, portal hypertension, and mesenteric slow flow vascular malformations.1 Omental infarction also has a higher male to female ratio of 2:1.2 There is no reported association with risk factors for thromboembolism. Omental infarction is noted in multiple case reports to be associated with constipation, but statistical correlation has not been established. The etiology of omental infarction is presumed to be primarily idiopathic, and likely pathophysiology is secondary to increased perivascular fat in the omentum limiting blood supply. Because of the increased fat accumulation, the increased weight of the omentum is thought to lead to increased distal omental torsion.3 The predominance of right sided omental infarctions as opposed to left sided infarcts can be attributed to the anatomically altered right sided omental vasculature, possibly due to underlying structures and increased length and mobility of the right omentum that has decreased ability to resist spontaneous torsion, infarction, or venous stasis.4Omental infarction, which can closely mimic appendicitis, should be considered in overweight patients, especially in those with a history of chronic constipation. Abdominal ultrasound, with a reported sensitivity of 60% to 80%, is the preferred initial imaging modality. One key diagnostic clue on ultrasound is the “tethered fat sign,” first described in 2020 by Esposito et al,2 which refers to an immobile mass affixed to the abdominal wall that does not move with respiration. If the ultrasound results are inconclusive, clinically stable patients may proceed to a CT scan, which has a higher sensitivity (90%) and is regarded as the gold standard for diagnosis. In some cases, the diagnosis may only be made intraoperatively during an appendectomy.Omental infarction is typically self-limiting and managed conservatively with anti-inflammatory medications and fluid therapy as needed based on clinical presentation. Although prophylactic antibiotics have been described in literature, this is not consistently prescribed as a standard of care. Surgical intervention before diagnosis occurs most typically secondary to presumed appendicitis. Once a normal appendix has been revealed, the surgeon typically then resects the infarcted portion of the omentum. Minimal omentectomy surgical complications have been documented in literature. Primary omentectomy for omental infarction is reserved for patients who have not responded to conservative management or become clinical unstable.5 Long-term prognosis is unknown; however, omental infarction is believed to be benign and self-limiting with symptom resolution without reported long term complications.6Because of complicated cases of omental infarction requiring surgical intervention, pediatric surgery was consulted. A conservative treatment approach was pursued following shared decision-making between family, surgery, and hospitalist teams. She was admitted for observation overnight and remained hemodynamically and clinically stable with some improvement in pain. This included pain control with scheduled acetaminophen, ibuprofen, and management of constipation with stool softeners. The patient received one dose of morphine for pain during her admission. Opioid medications were avoided given history of constipation and known side effect with the medication class. Her rebound tenderness resolved at time of discharge. Her family was counseled on the use of non-steroidal anti-inflammatory agents (NSAIDs), as needed for pain management, and educated that pain uncontrolled on NSAIDs alone would warrant further evaluation. The family was given recommendations for constipation management and instructed to follow up with their primary care physician 1 to 2 days following discharge. Additionally, she was referred to follow up with a pediatric gastroenterologist in 2 to 3 months. The patient has not had any readmissions for this condition over the past two years. She currently continues to be managed for chronic constipation.Omental infarction should be considered on the differential for acute right sided abdominal pain, especially in patients with risk factors of overweight/obesity or constipation.Ultrasound is the primary imaging modality for diagnosis, and CT may be used for further specification and is the gold standard for diagnosis.Patients with omental infarction can be managed conservatively, although refractory cases may require surgical intervention or antibiotics.