Bloody Stools in a 2-month-old Infant

An 11-week-old boy born at 29 weeks’ gestation presents to the emergency department (ED) with a 1-day history of blood-streaked stool. The patient started having frequent loose stool with mucus throughout the day. He was sleeping more but tolerating feeds well, with no irritability, vomiting, or worsening reflux. He had no fever at home and no sick contacts.The patient’s medical history is significant for a 7-week NICU admission with respiratory distress syndrome requiring surfactant administration and intubation for a week before being transitioned to noninvasive mechanical ventilation and eventually room air. During his NICU stay he exhibited symptoms consistent with gastroesophageal reflux, which led to a suspicion of cow milk protein intolerance (CMPI); a decision was made to change from human milk to an exclusive extensively hydrolyzed protein formula. There was no blood in the stool at that time, and necrotizing enterocolitis was not suspected. At 7 weeks of age, the patient was doing well and subsequently was transferred from the NICU to the inpatient care unit for the advancement of enteral nutrition. He was discharged from the hospital at 9 weeks of age. At the time of discharge, he was tolerating full oral feedings, weighed 2,500 g, and measured 48 cm (10th and 40th percentiles, respectively, on the Fenton preterm growth chart). The patient remained exclusively on hydrolyzed formula, with no discomfort noted. Two weeks later he presents to the ED with blood-streaked stool.The patient is appropriately immunized: he received his vaccines in the hospital at 8 weeks of age, including the rotavirus vaccine. He is receiving daily supplements of vitamin D and ferrous sulfate and is not currently receiving any additional medications. There is no history of recent travel or exposure to individuals from international locations, and the patient’s diet is exclusively composed of formula. There is no notable familial history of gastrointestinal (GI) illness, except for a maternal cousin with CMPI.During the patient’s ED visit, he is found to have blood-streaked stool; his initial vital signs are within normal limits, with a temperature of 99.1°F (37.3°C), a heart rate of 170 beats/min, and a respiratory rate of 44 breaths/min, with oxygen saturation of 97%. His weight is 3,000 g (20th percentile), and he appears well and alert, without any signs of poor perfusion. The abdominal examination findings are normal. The perianal region is observed to have mild erythema, with no evidence of an anal fissure. No further rectal examination is performed. During routine measurement of vital signs while in the ED, an isolated episode of fever is noted, with a temperature of 100.4°F (38.0°C).Initial investigations include normal urine analysis findings, an elevated C-reactive protein level (3.98 mg/dL [39.8 mg/L]) (reference range, 0–0.50 mg/dL [0–5.00 mg/L]), a low white blood cell count (1,700/µL [1.7 × 109/L]) (reference range, 5,000–17,500/μL [5.0–17.5 × 109/L]), a low neutrophil count (660/µL [0.66 × 109/L]) (reference range, 800–8,400/μL [0.8–8.4 × 109/L]), and normocytic anemia with a hemoglobin level of 9.2 g/dL (92 g/L) (reference range, 9.5–13.5 g/dL [95–135 g/L]). Capillary blood gas, lactate, and electrolyte levels are normal.A plain abdominal film obtained is concerning for gaseous distention and bowel wall thickening; however, no pneumatosis intestinalis, portal gas, or free air is seen. Abdominal ultrasonography reveals minimal nonspecific abdominopelvic free fluid, with no ileocolic intussusception. A GI specialist asks for stool testing, and the results reveal the diagnosis.Common etiologies for bloody stools in an 11-week-old infant include allergic colitis and infectious enterocolitis. (1)(2)(3) Allergic colitis secondary to CMPI has an estimated prevalence of 3% in developed countries (1); CMPI can present with occult or overt lower GI bleeding and diarrhea. (2) This patient had been previously diagnosed as having CMPI and had been on hydrolyzed formula exclusively. Although an extensively hydrolyzed formula is not always sufficient to treat CMPI, the acute presentation seemed unlikely due to CMPI in the setting of an unchanged diet. The tetrad of acute lower GI bleed, diarrhea, elevated inflammatory markers, and one episode of fever in the ED was concerning for an infectious etiology.Most cases of infectious gastroenteritis in children worldwide are caused by noroviruses and rotaviruses (3); therefore, the patient was initially suspected to have viral gastroenteritis, and an infectious evaluation including stool and blood cultures was not performed in the ED. However, despite the pathogens’ damage to the small bowel enterocytes, viral gastroenteritis does not usually present with bloody stool. (3) Bacterial colitis accounts for most cases of acute bloody diarrhea. (4) The most common pathogens that can lead to lower GI bleed in children include Salmonella, Shigella, Campylobacter, Escherichia coli, and Yersinia. Less common are viruses such as adenovirus and cytomegalovirus, and with a positive traveling history, parasites. (5)On admission to the pediatric inpatient unit, bacterial colitis was suspected over a viral etiology in light of the elevated inflammatory markers, low white blood cell count, and persistent bloody stool. Therefore, blood and stool cultures were sent on day 1 of admission, and intravenous ampicillin and tobramycin were initiated.Clinical improvement was noticed while taking antibiotics, with resolving bloody stool and increased energy. On day 3 of admission, the bloody stools had resolved, the repeated abdominal film showed an improvement in gas distention, and the blood cultures had no bacterial growth. Diarrhea progressively improved, with complete resolution on day 7 of admission.On day 5 of admission, the stool culture grew Salmonella enterica subsp enterica Group H(O:6,14) Florida, classified as a nontyphoidal Salmonella (NTS). Although contaminated food and water can be a cause of NTS, our patient was exclusively formula fed. Furthermore, the formula was prepared with municipal water where there were no known cases of waterborne Salmonella. Further questioning with the family revealed household exposure to reptiles, which was deemed to be the likely source of NTS; the father had two corn snakes that lived in the home and were allowed out of their terrarium.The species S enterica is divided into more than 2,500 serovars, which are further classified into typhoidal Salmonella and NTS. The latter has a large range of vertebrate hosts, making it a primarily zoonotic disease in the developed world. (6)Nontyphoidal Salmonella is found in inadequately cooked poultry, pork, and beef, as well as in asymptomatic carriers, including reptiles (such as turtles and snakes), amphibians, rodents, and, less frequently, cats and dogs. (7)(8) Exposure to the reptile’s environment (eg, surfaces contaminated with feces) is sufficient for infection to occur, and direct contact is not required. (9)Nontyphoidal Salmonella invades the lining of the small and large intestines and triggers inflammation, leading to abdominal pain, fever, bloody (or nonbloody) diarrhea, and elevated inflammatory markers. It is important to note that infants do not have a strong inflammatory response and can present without fever and normal inflammatory markers. (10) Occasionally, NTS can result in invasive disease such as bacteremia, meningitis, and encephalopathy, with the highest incidence among children who are immunocompromised, asplenic, or younger than 3 months. (3)(8)Antibiotics are recommended for patients at high risk for invasive disease (all immunocompromised children and infants <3 months of age) but are generally not used in healthy children older than 3 months presenting with uncomplicated NTS. (8)(10) Ampicillin or trimethoprim-sulfamethoxazole can be used for known susceptible strains. (11) Treating uncomplicated NTS enterocolitis in high-risk patients presents a challenge due to the lack of clear guidelines on the optimal treatment duration. (11)(12) Different recommendations suggest 5 to 14 days. However, a recent study by Mori et al (13) highlights the possibility of relapse in immunosuppressed patients who receive less than 10 days of antimicrobial therapy for uncomplicated NTS. The patient in this case was sensitive to both antibiotics and was continued on intravenous ampicillin for 7 days, followed by 7 days of amoxicillin. In Canada, managing Salmonella infection involves not only treatment but also reporting the disease to provincial health authorities. Both NTS and typhoid Salmonella are listed as notifiable diseases to identify potential contamination and prevent further spread of the disease. In this case, the provincial health authority was informed of the infection as soon as a positive stool culture was confirmed. (14)Even in exclusively breastfed or formula-fed infants, reptiles in the home can be a source of Salmonella enterocolitis.Ask about reptiles in the homes of infants and children who present with bloody diarrhea.Elevated inflammatory markers are not usually seen with cow milk protein intolerance.

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