Last reviewed: March 2026Contents
MDM Templates
NVD NOS / Acute Gastroenteritis
Patient with nausea, vomiting, diarrhea most consistent with simple acute gastroenteritis given the acute onset, lack of peritoneal signs, and absence of high-risk features.
Exam reassuring: They are nontoxic appearing with stable vitals, and a benign abdominal exam.
No high risk features for invasive pathogens: No bloody stools, no high fever, no immunocompromised state.
History, exam, and workup lower suspicion for emergent etiologies including small bowel obstruction, appendicitis, bowel ischemia, pancreatitis, DKA, ACS, and other acute abdomen.
Reassessment: After treatment patient is tolerating PO fluids with improvement in symptoms.
Disposition: Discharge with PCP follow-up within 48 hours. Return precautions for inability to tolerate PO, bloody stools, worsening abdominal pain, fever, or signs of dehydration.
Admit if: PO intolerance despite aggressive ED treatment, significant dehydration, electrolyte derangement, concern for surgical abdomen, or high-risk patient (elderly, immunocompromised).
Hyperemesis Gravidarum
Pregnant patient at *** weeks gestation presenting with persistent nausea and vomiting with inability to tolerate PO.
No vaginal bleeding, no abdominal pain concerning for ectopic or placental abruption.
Vitals stable.
History and exam lower suspicion for molar pregnancy, ectopic pregnancy, appendicitis, ovarian torsion, pyelonephritis, DKA, and other emergent causes of vomiting in pregnancy.
Plan: IV hydration, thiamine 100mg IV (before dextrose), ondansetron / metoclopramide. Patient tolerating PO after treatment.
Disposition: Discharge with OB follow-up within 24-48 hours. Home regimen: B6 25mg PO TID +/- doxylamine 12.5mg, ginger 250mg QID, small frequent meals, switch to prenatal vitamin without iron.[1]
Admit if: Refractory vomiting, severe dehydration, electrolyte abnormalities (hypokalemia, hyponatremia), weight loss >5% body weight, or ketonuria.
Cannabinoid Hyperemesis Syndrome
Patient with cyclic vomiting in the setting of chronic daily cannabis use. Presentation consistent with cannabinoid hyperemesis syndrome given the characteristic pattern, compulsive hot-water bathing behavior, and absence of alternative etiology. Nontoxic appearing with stable vitals.
History and exam lower suspicion for CVS, DKA, SBO, pancreatitis, adrenal crisis, and other emergent causes of cyclic vomiting.
Plan: Haloperidol 5mg IV/IM, capsaicin cream 0.075% applied to abdomen. IV hydration. Symptoms controlled in ED.[2]
Disposition: Discharge with counseling on cannabis cessation as the only definitive treatment. PCP follow-up.
C. Difficile Colitis
Patient with watery diarrhea in the setting of recent antibiotic use / hospitalization / advanced age. Presentation most consistent with C. difficile colitis. No peritoneal signs, no significant abdominal distension, no hemodynamic instability. Low suspicion for toxic megacolon, SBO/LBO, IBD flare, bowel ischemia, or other acute abdomen.
Non-severe (WBC <15, Cr <1.5):
Plan: Discontinue offending antibiotic. Oral vancomycin 125mg QID x 10 days (preferred over metronidazole per current guidelines). C. diff toxin sent.[3]
Disposition: Discharge with PCP/GI follow-up.
Severe (WBC >15, Cr >1.5x baseline, or age >65 with significant comorbidities):
Plan: Oral vancomycin 125mg QID. Consider adding IV metronidazole 500mg q8h if fulminant. Lactate, CBC, BMP. CT abdomen/pelvis if concern for complications.
Disposition: Admit.
Fulminant (hypotension, ileus, megacolon):
Plan: Vancomycin 500mg PO/NG QID + vancomycin 500mg PR q6h + metronidazole 500mg IV q8h. Surgical consult.[3]
Clinical Education
Antiemetic Selection
| Agent | Dose | Pearl |
| Ondansetron | 4mg IV/ODT | 4mg = 8mg in efficacy; 8mg adds QTc risk without benefit[4] |
| Metoclopramide | 10mg IV | Prokinetic — good for gastroparesis, post-surgical. EPS risk (give with diphenhydramine) |
| Prochlorperazine | 10mg IV | Often more effective than ondansetron for undifferentiated NVD. EPS risk[5] |
| Haloperidol | 2.5-5mg IV/IM | First-line for CHS. Excellent rescue antiemetic. QTc risk[2] |
| Droperidol | 0.625-1.25mg IV | Fast, potent. Black box for QTc is widely considered disproportionate to actual risk[6] |
| Dexamethasone | 8-10mg IV | Adjunct for refractory vomiting or cyclic vomiting. Reduces ED revisits[7] |
Antibiotics in Diarrhea
Most acute diarrhea is viral and self-limited — antibiotics are not indicated. Consider empiric antibiotics only for: severe disease (high fever, bloody stools, >6 stools/day), immunocompromised patients, or traveler’s diarrhea with significant symptoms.[8]
Traveler’s diarrhea: Azithromycin 1g PO x1 (preferred, especially SE Asia with fluoroquinolone resistance) or ciprofloxacin 750mg PO x1. Most cases resolve within 5 days without antibiotics — antibiotic benefit is shortening symptoms by 1-2 days.[8]
Bloody diarrhea: Avoid antibiotics empirically if STEC/EHEC (O157:H7) is suspected — antibiotics may increase HUS risk. Send stool cultures. If severely ill with dysentery, azithromycin or fluoroquinolone is reasonable while awaiting cultures.[8]
Hyperemesis Gravidarum Treatment Ladder
| Line | Agent | Dose | Notes |
| 1st (home) | Pyridoxine (B6) +/- Doxylamine | B6 25mg PO TID; Doxylamine 12.5mg PO QHS | OTC, first-line per ACOG |
| 2nd (ED) | Ondansetron | 4mg IV/ODT | Small cleft palate association in T1 — no proven causation |
| 2nd (ED) | Metoclopramide | 10mg IV | Prokinetic, give with diphenhydramine for EPS |
| 3rd | Methylprednisolone | 16mg PO/IV TID x 3d then taper | Refractory only — discuss with OB |
Also: ginger 250mg QID, switch prenatal vitamin to one without iron, avoid strong odors, small frequent meals.[1]
CHS Treatment
| Line | Agent | Dose |
| 1st | Haloperidol | 5mg IV/IM — more effective than ondansetron for CHS[2] |
| 1st | Capsaicin cream 0.075% | Apply to abdomen — relief within 30 min via TRPV1 receptor |
| Adjunct | Lorazepam | 1-2mg IV |
| Definitive | Cannabis cessation | Only cure — symptoms recur with resumed use |
Cyclic Vomiting Syndrome — Abdominal Migraine Cocktail
| Line | Agent | Dose |
| 1st | NS bolus (or D5NS if starvation ketosis) | 1-2L |
| Ondansetron | 4mg IV | |
| Sumatriptan | 6mg SQ | |
| Ketorolac | 30mg IV | |
| Magnesium sulfate | 1-2g IV | |
| 2nd | Chlorpromazine | 12.5-25mg IV |
| Haloperidol | 2.5-5mg IV | |
| 3rd | Ketamine | 10-20mg IV bolus +/- 20-30mg infusion over 1h |
Also consider famotidine 20mg IV or pantoprazole 40mg IV as adjunct.[9]
C. Diff Pearls
Oral vancomycin is now first-line for all C. diff — metronidazole is inferior and relegated to adjunctive role in fulminant disease only. Fidaxomicin 200mg BID x 10d is equivalent to vancomycin with lower recurrence rates but much more expensive.[3]
When to suspect: ≥3 unformed stools in 24 hours + risk factors (antibiotics within 90 days, hospitalization, age >65, PPI use). Do NOT test formed stools — false positives are common.
Toxic megacolon red flags: Colonic dilation >6cm on imaging, fever, tachycardia, leukocytosis (often >30k), AKI, lactic acidosis. Surgical consult for colectomy — mortality is high if delayed.[3]
References
- ACOG Practice Bulletin No. 189. Nausea and Vomiting of Pregnancy. Obstet Gynecol. 2018;131(1):e15-e30. PubMed
- Richards JR et al. Cannabinoid Hyperemesis Syndrome: Pathophysiology and Treatment in the Emergency Department. J Emerg Med. 2017;52(4):544-551. PubMed
- Johnson S et al. Clinical Practice Guideline by IDSA/SHEA: 2021 Focused Update on Management of C. difficile Infection in Adults. Clin Infect Dis. 2021;73(5):e1029-e1044. PubMed
- Freedman SB et al. Ondansetron Dosing in Emergency Department Patients. NEJM. 2015;372:2229-2239. PubMed
- Barrett TW et al. Prochlorperazine vs Ondansetron for Nausea and Vomiting in the ED. Acad Emerg Med. 2011;18(8):816-821. PubMed
- Gaw CM et al. Droperidol in the Emergency Department: A Systematic Review. Ann Emerg Med. 2020;75(3):346-356. PubMed
- Tavares T et al. Dexamethasone as Adjunct Therapy for Acute Gastroenteritis in the ED: A Systematic Review. CJEM. 2021;23(5):663-672. PubMed
- Shane AL et al. IDSA Clinical Practice Guidelines for the Diagnosis and Management of Infectious Diarrhea. Clin Infect Dis. 2017;65(12):e45-e80. PubMed
- Venkatesan T et al. Guidelines on Management of Cyclic Vomiting Syndrome in Adults by the American Neurogastroenterology and Motility Society. Neurogastroenterol Motil. 2019;31(Suppl 2):e13604. PubMed
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