Acute Abdominal Pain
Introduction
Why is abdominal pain important to pediatric surgeons?
Acute abdominal pain in children is one of the more frequent reasons for emergency room visits and pediatric surgical consultations. Acute appendicitis was responsible for nearly 90,000 pediatric emergency department visits during 2013 in the United States [1]. Both medical and surgical diagnoses present with acute abdominal pain and the incidence of these varies with age and gender.
What is the general approach to optimize diagnostic testing?
Through the assessment of symptoms (duration, intensity), physical exam findings and consideration of the incidence of specific etiologies, the differential diagnosis of acute abdominal pain can be narrowed to facilitate efficient use of diagnostic testing. This approach leverages pretest probability to increase the diagnostic yield of laboratory tests and imaging studies.
content in this topic is referenced in SCORE Abdominal Pain overview
Epidemiology
The most common surgical cause of abdominal pain in children is appendicitis. Other causes may be suspected based on symptoms and age.
What are the most common surgically treated causes of pediatric acute abdominal pain?
The most common surgical cause of acute abdominal pain in children is acute appendicitis. Within specific age groups other medical and surgical causes of acute abdominal pain should also be considered.
Age group | Diagnoses |
any age | intestinal malrotation/volvulus mechanical bowel obstruction
Meckel diverticulitis perforated viscus |
newborn | neonatal obstruction, congenital lesion internal hernia/volvulus– omphalomesenteric duct remnant, duplication cyst, mesenteric cyst incarcerated inguinal hernia |
infant | incarcerated inguinal hernia nonaccidental abdominal trauma Hirschsprungassociated enterocolitis abdominal/retroperitoneal neoplasm |
toddler | appendicitis– complicated non-accidental abdominal trauma Hirschsprungassociated enterocolitis abdominal/retroperitoneal neoplasm pneumonia |
pre-adolescent child |
gallstone complications – pigment gallstones
epiploic fat torsion/infarction omental torsion/infarction Henoch-Schonlein purpura viral gastroenteritis ovarian torsion (female) |
adolescent | gallstone complications – pigment and cholesterol gallstones
inflammatory bowel disease
ovarian pathology (female)
pelvic inflammatory disease(female) perforated gastric/duodenal ulcer epiploic fat torsion/infarction omental torsion/infarction Henoch-Schonlein purpura urinary tract infection urolithiasis |
Several factors such as season, region and race/ethnicity account for the variable incidence of some diagnoses. Viral infections associated with gastrointestinal symptoms typically occur seasonally and regionally [2]. Vaccination and indirectly, access to care may impact disease incidence. For example, rotavirus infection is most prevalent in areas where vaccination rates are low [3]. Race and/or ethnicity impacts the prevalence of conditions which indirectly lead to acute abdominal pain. Hemoglobinopathies which are more common in particular races or ethnic groups, such as sickle cell disease in African-Americans or thalassemia in individuals of Mediterranean descent, predispose to formation of pigment gallstones which in turn may cause acute abdominal pain (biliary colic, acute cholecystitis, choledocholithiasis, or gallstone pancreatitis).
Presentation
The initial presentation in patients with abdominal pain can be associated with obstruction, inflammation or both.
What features aid in characterizing abdominal pain?
When considering the underlying cause of acute abdominal pain in children the presenting symptoms, physical examination findings and initial laboratory studies can be grouped into patterns associated with intestinal obstruction, inflammatory processes or mixed obstructive/inflammatory presentation. By determining the pattern of abdominal pain and considering age, gender and comorbidities, the likely diagnoses can be narrowed. Confirmatory laboratory testing, imaging and initial treatment can then be tailored to the leading diagnoses.
Abdominal pain pattern | Diagnoses |
obstruction | congenital intestinal malrotation/volvulus internal hernia/volvulus omphalomesenteric duct remnant/Meckel diverticulum intestinal duplication cyst mesenteric cyst incarcerated inguinal hernia intraluminal obstruction functional obstruction
acquired adhesive bowel obstruction Crohn disease partial obstruction, stricture superior mesenteric artery syndrome intraluminal obstruction
|
inflammation |
gallstone complications
pancreatitis pelvic inflammatory disease other intestinal
perforated viscus peptic ulcer disease foreign bodies nonaccidental abdominal trauma pneumonia viral mesenteric adenitis/gastroenteritis |
obstruction and inflammation | intestinal obstruction with ischemic/infarcted bowel complicated appendicitis inflammatory bowel disease
functional obstruction
|
other | abdominal/retroperitoneal neoplasm ovarian pathology
epiploic fat torsion/infarction omental torsion/infarction (male>female) biliary dyskinesia gastroesophageal reflux |
What are the critical components of the history when evaluating a child with abdominal pain?
Because characteristics of abdominal pain are challenging to articulate the nature of the pain can be conveyed through a series of questions. The parents of younger children can provide insight based on their observations. It is often difficult for children younger than ten years to pin point their symptoms and they may only describe a generalized feeling of pain, nausea and discomfort. Relevant features of abdominal pain include
- abdominal pain features
- pattern – constant, intermittent
- character – dull, sharp, crampy
- intensity – increasing, stable/constant vs intermittent, decreasing; impact on normal activities
- location – migratory or consistent location, distribution
- associated symptoms
- nausea, emesis – emesis color
- diarrhea, constipation, obstipation; stool color/presence of blood
- constitutional – fever, malaise, lethargy
- other – cough, sore throat, dysuria
- duration (time from onset) and sequence of symptoms
- exacerbating and/or relieving factors
Emesis (especially if bilious), obstipation and intermittent abdominal pain imply presence of intestinal obstruction or disordered motility such as an ileus. Nonspecific symptoms such as fever, malaise and constant pain in a persistent location may be caused by inflammatory conditions. Cough, sore throat or dysuria suggests a potential medical cause of abdominal pain. Also important to assess is a prior history that includes comorbidities, previous symptoms, operations, ill contacts, recent travel and any trauma.
What are the critical parts of the physical exam when evaluating a child with abdominal pain?
A careful physical exam is essential but potentially challenging especially in young children. Observation of a child’s appearance and movement while obtaining his or her history provides insight into the degree of discomfort. Utilizing some means of distracting the sick child may be the only way to obtain a good abdominal exam. Warming the hands or examining younger children and infants while still clothed or in their parents arms may be necessary to help the child relax in order to allow the exam to proceed. Pertinent findings include distension and pain with palpation and/or percussion while noting the degree of tenderness and location. Adjunct maneuvers include assessing costovertebral angle tenderness and referred pain from costochrondritis as well as the presence of Rovsing, obturator and psoas signs. Other physical exam components may also support a non-abdominal source for symptoms such as diminished breath sounds for pneumonia or pharyngeal erythema/tonsillar enlargement with Streptococcal pharyngitis.
Assessment
Laboratory tests and imaging should be tailored to the history and exam findings.
What laboratory tests can help determine the type of abdominal pain and leading diagnoses?
Laboratory tests can help categorize the abdominal pain as possibly related to intestinal obstruction, inflammation, a combination of inflammation and obstruction or neither. Elevatations of white blood count (especially with neutrophilia), C-reactive protein or the erythrocyte sedimentation rate support an inflammatory process such as appendicitis, Meckel diverticulitis or intestinal perforation/peritonitis. Direct hyperbilirubinemia, elevated alkaline phosphatase or gamma-glutamyl transferase (GGT), mildly elevated aspartate transaminase (AST) and alanine transaminase (ALT) are suggestive of biliary obstruction whereas marked transaminase elevation implies hepatic inflammation or hepatocellular damage (ischemia/reperfusion, toxin exposure). Amylase and lipase elevation are encountered with pancreatitis and the urinalysis may point to a genitourinary source.
Type of gall bladder disease | Presentation |
biliary colic | intermittent mild to moderate right upper quadrant (RUQ) pain nausea alone may be presenting symptom normal labs |
cholecystitis | severe right upper quadrant pain/tenderness, fever increased alkaline phosphatase, GGT, WBC |
choledocholithiasis | right upper quadrant pain, jaundice increased bilirubin (direct)/AST/ALT/alkaline phosphatase, GGT fever (cholangitis) |
gallstone pancreatitis | right upper quadrant/epigastric pain, radiation to back increased amylase, lipase transient increase in bilirubin (direct)/AST/ALT/ alkaline phosphatase |
What imaging is most appropriate for the leading diagnoses?
The potential diagnostic contribution of imaging can be increased by considering the potential relevant findings and predictive value of the study for the leading diagnosis.
- abdominal radiograph
- intestinal perforation
- intestinal obstruction, ileus
- upper gastrointestinal series (UGI)/small bowel follow-through (SBFT)
- intestinal malrotation
- mechanical bowel obstruction
- superior mesenteric artery syndrome
- adhesive bowel obstruction
- Crohn disease
- abdominal/pelvic ultrasound
- intussusception
- appendicitis
- abdominal/retroperitoneal/pelvic mass
- intestinal duplication cyst
- mesenteric cyst
- neoplasm
- gall bladder disease
- renal pathology
- ovarian pathology (cyst, torsion)
- abdominal/pelvic computerized tomography (CT)
- intestinal perforation
- intestinal obstruction
- appendicitis (American College of Radiology has recommended use of ultrasound prior to CT for evaluation of right lower abdominal pain in children to minimize radiation exposure [4])
- abdominal/retroperitoneal/pelvic mass
- intestinal duplication cyst
- mesenteric cyst
- neoplasm
- Crohn disease, colitis
- pancreatitis
- hepatic pathology
- renal pathology
- abdominal/pelvic magnetic resonance imaging (MRI)/enterography
- appendicitis
- Crohn disease, colitis
- abdominal MRI/magnetic resonance cholangiopancreatography
- hepato-pancreatico-biliary pathology
Image modality | Key findings | Associated diagnoses |
abdominal radiograph | normal bowel gas pattern | constipation appendicitis |
gastric distension | gastroenteritis | |
loss of psoas shadow focal ileus scoliosis fecalith | appendicitis | |
bowel dilation predominantly left upper quadrant | proximal small bowel obstruction gastroenteritis pancreatitis | |
bowel dilation except right lower quadrant | ||
paucity of gas in right lower quadrant/ascending colon adipose rose sign | ||
displacement of bowel loops | abdominal/retroperitoneal mass | |
diffuse bowel dilation | gastroenteritis or other ileus (pneumonia, urinary tract infection) | |
colonic air fluid levels | gastroenteritis | |
pneumatosis | neutropenic enterocolitis | |
colon cut off sign | Hirschsprung associated enterocolitis appendicitis | |
pneumoperitoneum | perforated viscus (gastric/duodenal ulcer, Meckel diverticulum, intestinal perforation due to non-accidental trauma, perforated appendicitis (rare)) | |
Upper gastrointestinal series +/- small bowel follow through | delayed passage of contrast from stomach | gastroenteritis |
bird beak in proximal duodenum | ||
dilated proximal duodenum, delayed contrast passage across vertebral body | ||
Contrast enema | inspissated stool | |
saw toothing of colon | colitis | |
Ultrasound | target sign | |
non-compressible tubular structure in right lower quadrant (greater than 7 mm diameter) | ||
loculated/complex pelvic fluid with hyperemia | complicated appendicitis pelvic inflammatory disease | |
inversion of mesenteric vessels | ||
gall bladder wall thickening, pericholecystic fluid, sonographic Murphy sign | ||
bile duct dilation | choledocholithiasis | |
pancreatic edema, peripancreatic fluid | pancreatitis | |
pelvic fluid, decompressed ovarian cyst | ||
ovarian enlargement, hypoperfusion | ||
cystic lesion (thick walled – bowel signature) | ||
cystic lesion (thin walled) | ||
echogenic fat - ovoid | epiploic fat torsion | |
echogenic fat – swirling blood vessels anterior to bowel, right greater than left | omental torsion | |
Computerized tomography/magnetic resonance imaging | pancreatic edema, hypoperfusion, peripancreatic fluid | pancreatitis |
bowel wall thickening, phlegmon, abscess | ||
small bowel dilation, transition zone | ||
whirlpool sign |
What is the role of clinical scores in determining the diagnosis?
The Alvarado Score [5] and Pediatric Appendicitis Score (PAS) [6] combine symptoms (abdominal pain migration, anorexia, nausea/vomiting), signs (right lower quadrant tenderness, signs of peritoneal irritation by rebound or percussion tenderness, fever) and laboratory results (white blood count, percent neutrophils or absolute neutrophil count) to estimate likelihood of appendicitis in children.
In the initial report regarding the PAS, Samuels noted the prospective sensitivity to be 1, specificity 0.87, positive predictive value 0.90 and negative predictive value 1 with a cutoff point of greater than or equal to eight for appendicitis and less than or equal to five for not being appendicitis. Patients scoring six to seven were unclear [6]. Alvarado did not report initial thresholds for high or low likelihood of appendicitis. Multiple investigators have studied potential cut points primarily in children’s hospitals [7][8]. The scores may perform differently in a community hospital setting. Most studies report a mid-range of scores which lack sufficient predictive value. Rather these scores are used to indicate need for further studies (e.g. imaging).
Alvarado | PAS | ||||
Predictor | Detail | Value | Detail | Value | |
symptoms | migration | 1 | 1 | ||
anorexia | 1 | 1 | |||
nausea-vomiting | 1 | 1 | |||
signs | tenderness right lower quadrant | 2 | 2 | ||
rebound pain | rebound | 1 | cough/ percussion/ hopping | 2 | |
fever | ≥37.3 ○C | 1 | ≥38.0 ○C | 1 | |
laboratory | leukocytosis | ≥10,000/mm3 | 2 | ≥10,000/mm3 | 1 |
neutrophilia | ≥75% | 1 | ≥7500/mm3 | 1 | |
total | 10 | 10 | |||
Additional attempts to develop predictive tools have been hampered by poor inter-rater reliability for examination findings [9]. Kharbanda developed an algorithm to identify children at low risk for appendicitis with the goal of eliminating unnecessary diagnostic imaging for children [10]. The algorithm was refined and tested prospectively at multiple institutions and the components included absolute neutrophil count (ANC), right lower quadrant (RLQ) tenderness and pain with walking, jumping or coughing.
- ANC ≤6750/mm3 and
- No maximal tenderness in RLQ
- or
- Maximal tenderness in RLQ, but no abdominal pain with walking/jumping/coughing
- No maximal tenderness in RLQ
For children designated as not having appendicitis the sensitivity was 98.1% (97.0 to 98.9), specificity 23.7% (21.7 to 25.9), negative predictive value 95.3% (92.3 to 97.0) and positive predictive value 44.9% (42.8 to 47.0).
Medical Treatment
Dehydrated patients should be resuscitated during the initial evaluation and throughout serial clinical monitoring.
How should patients be managed while the diagnosis is uncertain?
When the etiology accounting for acute abdominal pain is not clearly established during the initial evaluation serial observation of a child’s symptoms and physical exam evolution can be valuable to distinguish surgical from nonsurgical etiologies. Outpatient observation is reasonable for the child with mild symptoms and easy access to medical care. Those children whose symptoms are more severe or worrisome as well as those with poor access to medical care require hospitalization with administration of intravenous fluids and bowel rest (especially if symptoms follow an obstructive pattern, i.e. abdominal distension, emesis, obstipation). Improvement in symptoms points to a self limited process (such as viral gastroenteritis), whereas failure to improve and a worsening clinical exam indicate a need to further investigate the source of abdominal pain.
What are the medically treated causes of acute abdominal pain which are difficult to distinguish from those treated surgically?
The differential diagnosis of a child with acute abdominal pain includes disorders which are primarily treated nonoperatively. By organ system/region these include
- abdominal/gastrointestinal
- viral gastroenteritis, mesenteric adenitis
- infectious colitis
- Henoch-Schonlein purpura
- inflammatory bowel disease (Crohn, ulcerative colitis)
- pancreatitis
- omental, epiploic fat infarct
- genitourinary
- urinary tract infection
- pelvic inflammatory disease
- ovarian cyst
- on-abdominal
- Streptococcal pharyngitis
- pneumonia (right lower lobe)
Indications for Surgery
Patients with evidence of complete intestinal obstruction, peritonitis or a diagnosis of a surgical etiology should be explored.
What are the indications for operative exploration?
Indications for operative exploration can be categorized in the context of presenting symptoms and suspected diagnosis:
- evidence of complete bowel obstruction, intestinal volvulus, or vascular compromise of abdominal structures
- malrotationwith bilious emesis
- closed loop bowel obstruction (e.g. postoperative adhesions, omphalomesenteric duct remnant, intestinal duplication cyst)
- non-reducible intussusception
- ovarian torsion
- acute abdomen/peritonitis, intestinal perforation
- perforated duodenal ulcer
- intestinal perforation/necrosis
- perforated appendicitis, Meckel diverticulitis with diffuse peritonitis
- perforated Crohn disease
- toxic megacolon (ulcerative colitis, antibiotic-associated colitis)
- diagnosis of surgical etiology
- appendicitis
- cholecystitis, complicated gallstone disease (choledocholithiasis, gallstone pancreatitis)
- Meckel diverticulitis
- intestinal mass (duplication cyst, mesenteric cyst, intussusception with suspected pathologic lead point)
Surgical intervention for omental epiploic fat torsion/infarction is controversial.
The nonoperative treatment of acute appendicitis is currently being investigated (see Appendicitis Medical Treatment). The need for interval appendectomy after nonoperative treatment of complicated appendicitis is also under investigation (see Appendicitis Indications for Surgery).
Surgical Decision Making
What is the role of diagnostic laparoscopy?
Despite the availability of advanced imaging the cause for acute abdominal pain is not always identified. In cases where symptoms are persistent or worsening, laparoscopy may serve as a diagnostic adjunct and provide potential for definitive treatment when a surgical etiology is identified [11].
Research and Future Directions
What decision aids might expedite the diagnosis of appendicitis?
Because of the varied presentation and potential diagnosis associated with pediatric acute abdominal pain, methods to increase diagnostic efficiency (speed, reduction of abdominal CT scans, accuracy) have been investigated. Expediting diagnosis of acute appendicitis has been explored both through serologic testing and integration of diagnostic methods (clinical scores and imaging). Biomarkers such as urine leucine–rich α-2-glycoprotein (LRG), serum C-reactive protein (CRP) and procalcitonin have been investigated as a method to distinguish appendicitis from other diagnoses and gauge appendicitis severity [12][13][14]. Other strategies to expedite diagnosis combine biomarkers, clinical prediction scores and imaging or automate risk estimation through use of the electronic medical record [15][16].
Perspectives and Commentary
To submit comments about this topic please contact the editors at think@apsapedsurg.org.
Resident and Students
see Acute Abdominal Pain in the Resident and Student Handbook
Additional Resources
APSA Standardized Toolbox of Education for Pediatric Surgery (STEPS) presentation on Appendicitis
Discussion Questions and Cases
To submit interesting or controversial cases which display thoughtful patient management please contact the editors at think@apsapedsurg.org.
Discussion questions in SCORE Abdominal Pain conference prep
References
- HCUP Nationwide Emergency Department Sample (NEDS) 2013. Healthcare Cost and Utilization Project (HCUP), Agency for Healthcare Research and Quality. Available at: http://hcupnet.ahrq.gov/HCUPnet.jsp; accessed Dec. 31, 2015
- Thongprachum A, Takanashi S, Kalesaran AF, et al. Four-year study of viruses that cause diarrhea in Japanese pediatric outpatients. J Med Virol. 2015;87(7):1141-8. [PMID:25881021]
- Sahni LC, Tate JE, Payne DC, et al. Variation in rotavirus vaccine coverage by provider location and subsequent disease burden. Pediatrics. 2015;135(2):e432-9. [PMID:25583918]
- American College of Radiology ACR Appropriateness Criteria. Right Lower Quadrant Pain—Suspected Appendicitis. Available at: https://acsearch.acr.org/docs/69357/Narrative; accessed Dec. 31, 2015
- Alvarado A. A practical score for the early diagnosis of acute appendicitis. Ann Emerg Med. 1986;15(5):557-64. [PMID:3963537]
- Samuel M. Pediatric appendicitis score. J Pediatr Surg. 2002;37(6):877-81. [PMID:12037754]
- Goldman RD, Carter S, Stephens D, et al. Prospective validation of the pediatric appendicitis score. J Pediatr. 2008;153(2):278-82. [PMID:18534219]
- Bhatt M, Joseph L, Ducharme FM, et al. Prospective validation of the pediatric appendicitis score in a Canadian pediatric emergency department. Acad Emerg Med. 2009;16(7):591-6. [PMID:19549016]
- Kharbanda AB, Stevenson MD, Macias CG, et al. Interrater reliability of clinical findings in children with possible appendicitis. Pediatrics. 2012;129(4):695-700. [PMID:22392173]
- Kharbanda AB, Dudley NC, Bajaj L, et al. Validation and refinement of a prediction rule to identify children at low risk for acute appendicitis. Arch Pediatr Adolesc Med. 2012;166(8):738-44. [PMID:22869405]
- Hoffenberg EJ, Rothenberg SS, Bensard D, et al. Outcome after exploratory laparoscopy for unexplained abdominal pain in childhood. Arch Pediatr Adolesc Med. 1997;151(10):993-8. [PMID:9343009]
- Kentsis A, Ahmed S, Kurek K, et al. Detection and diagnostic value of urine leucine-rich α-2-glycoprotein in children with suspected acute appendicitis. Ann Emerg Med. 2012;60(1):78-83.e1. [PMID:22305331]
- Huckins DS, Simon HK, Copeland K, et al. A novel biomarker panel to rule out acute appendicitis in pediatric patients with abdominal pain. Am J Emerg Med. 2013;31(9):1368-75. [PMID:23891596]
- Gavela T, Cabeza B, Serrano A, et al. C-reactive protein and procalcitonin are predictors of the severity of acute appendicitis in children. Pediatr Emerg Care. 2012;28(5):416-9. [PMID:22531196]
- Zouari M, Jallouli M, Louati H, et al. Predictive value of C-reactive protein, ultrasound and Alvarado score in acute appendicitis: a prospective pediatric cohort. Am J Emerg Med. 2015. [PMID:26577432]
- Deleger L, Brodzinski H, Zhai H, et al. Developing and evaluating an automated appendicitis risk stratification algorithm for pediatric patients in the emergency department. J Am Med Inform Assoc. 2013;20(e2):e212-20. [PMID:24130231]
Media
malrotation with volvulus
Abdominal radiograph in two week old baby with malrotation/volvulus
malrotation with volvulus
Tapering duodenum in child with malrotation/volvulus
intestinal obstruction
Computerized tomography scan showing distal intestinal obstruction; etiology was omphalomesenteric duct remnant (Meckel diverticulum) adherent to umbilicus
distal small bowel obstruction
Abdominal radiograph showing dilated loop of small bowel consistent with distal small bowel obstruction; baby had an incarcerated right inguinal hernia.
appendicitis
Ultrasound showing dilated tubular structure in right lower quadrant with hyperemia by Doppler; structure was noncompressible
distal intestinal obstruction syndrome
Water-soluble contrast enema in a child with cystic fibrosis and abdominal pain; inspissated stool was evacuated.
intussusception
Paucity of bowel gas in toddler with severe, colicky abdominal pain; intussusception was identified by ultrasound.
intussusception
Ultrasound showing "target" sign in toddler with intussusception
mesenteric cyst
Ultrasound showing thin-walled cystic abdominal mass which on additional images was bilobed
ruptured ovarian cyst
Ultrasound showing enlarge ovary without perfusion; during laparoscopy for presumed ovarian torsion, ruptured hemorrhagic cyst was found.
ovarian torsion
Ultrasound showing enlarged ovary without blood flow; ovarian torsion identified on laparoscopy.
intestinal volvulus
Computerized scan demonstrating swirling of mesenteric blood vessels; during laparoscopy, segmental jejunal volvulus identified due to jejunal duplication cyst.
necrotizing enterocolitis
Abdominal radiograph showing pneumatosis intestinalis of ascending colon
Hirschsprung associated enterocolitis
Abdominal radiograph showing diffuse colon dilation without rectal gas in infant who underwent endorectal pullthough procedure for Hirschsprung disease
perforated viscus
Abdominal radiograph shows free intraperitoneal air in fussy infant; on laparoscopy, perforated Meckel diverticulum was found.
cholecystitis
Ultrasound reveals gall bladder full of stones with gall bladder wall thickening.
intestinal duplication cyst
Ultrasound shows large intraabdominal cyst with slightly thick wall; jejunal duplication cyst found on laparoscopy
Crohn disease
Computerized tomography scan shows thickening of terminal ileum without surrounding fat stranding or fluid collection
superior mesenteric artery syndrome
Abdominal radiograph shows markedly distended, fluid-filled stomach
superior mesenteric artery syndrome
Upper gastrointestinal series shows enlarged stomach, dilated proximal duodenum with delayed contrast passage across vertebral body into decompressed duodenum
colitis
Abdominal radiograph showing "thumb-printing" of the ascending colon in teenage girl with infectious colitis; she developed hemolytic uremic syndrome.