I have recurrent diarrhea and vomiting that begin in the luteal phase before each menstrual period; what is the likely cause and how should it be evaluated and managed?

Catamenial Cyclic Vomiting Syndrome

Your recurrent diarrhea and vomiting occurring specifically during the luteal phase before menstruation most likely represents catamenial cyclic vomiting syndrome (CVS), a hormone-triggered variant of CVS that requires both abortive therapy during prodromal symptoms and hormonal suppression with GnRH analogs for definitive control.

Diagnostic Approach

Screen for cannabis use immediately, as use >4 times weekly for >1 year suggests cannabinoid hyperemesis syndrome rather than CVS and requires 6 months of cessation to differentiate. 1, 2

Your symptoms should meet CVS diagnostic criteria: stereotypical episodes of acute-onset vomiting lasting <7 days, at least 3 discrete episodes in the past year with 2 in the prior 6 months, separated by at least 1 week of baseline health between episodes. 1, 2 The key distinguishing feature in your case is the strict temporal relationship to the luteal phase, which strongly suggests hormone-triggered CVS. 3

Required Initial Workup

• Complete blood count, serum electrolytes, glucose, liver function tests, lipase 1, 2
• Urine drug screen (specifically for cannabis) 1, 2
• Mid-luteal phase progesterone level (days 19-23 of cycle): if <6 nmol/L, this indicates anovulation and requires investigation for PCOS, hypothalamic amenorrhea, or hyperprolactinemia 4
• If progesterone is low: measure LH, FSH, testosterone, prolactin, androstenedione, DHEAS, and obtain pelvic ultrasound 4

Immediate Management Strategy

Abortive Therapy (First-Line)

You must learn to recognize your prodromal symptoms (impending doom, panic, anxiety, diaphoresis, flushing, mental fog, restlessness, headache, or bowel urgency) as the probability of aborting an episode is highest when medications are taken immediately at symptom onset. 1, 2

At the first sign of prodromal symptoms:

• Sumatriptan 20 mg intranasal spray (can repeat once after 2 hours, maximum 2 doses per 24 hours) 1
• Ondansetron 8 mg sublingual every 4-6 hours 1
• Administer sumatriptan in a head-forward position to optimize nasal receptor contact 1

Hormonal Suppression (Definitive Treatment)

GnRH analogs are the most effective treatment for cyclic symptoms during the luteal phase and should be initiated during days 1-3 of your cycle. 4, 3 A case report demonstrated complete symptom resolution for 5 years with subcutaneous goserelin (a GnRH analog) plus oral estrogen in a patient with identical catamenial CVS. 3

• Start GnRH analog (e.g., goserelin subcutaneous injection or leuprolide) on days 1-3 of cycle 4, 3
• Add low-dose estradiol patch after ~3 months to prevent menopausal symptoms and bone loss 4
• Prolonged GnRH analog use downregulates gonadotropin receptors, preventing ovulation and corpus luteum formation, thereby eliminating the hormonal trigger 4

Prophylactic Therapy (If Hormonal Suppression Declined)

If you prefer not to use hormonal suppression or while awaiting its initiation:

• Amitriptyline 25 mg at bedtime, titrating up to 75-150 mg nightly (goal dose 1-1.5 mg/kg) 1
• Obtain baseline ECG due to QTc prolongation risk 1
• Response rate is 67-75% 1

Emergency Department Management

If you present during an active episode:

• Aggressive IV fluid replacement with dextrose-containing fluids for rehydration and metabolic support 1
• Ondansetron 8 mg IV every 4-6 hours 1
• IV ketorolac 15-30 mg every 6 hours (maximum 5 days, daily maximum 120 mg) for abdominal pain—avoid opioids as they worsen nausea 1
• IV benzodiazepines for sedation in a quiet, dark room 1
• Droperidol or haloperidol for refractory cases 1

Essential Comorbidity Screening

Screen for anxiety, depression, and panic disorder, as these are present in 50-60% of CVS patients, and treating underlying anxiety can decrease episode frequency. 1, 2 This is particularly important given the panic and anxiety symptoms that often occur during the prodrome. 1, 2

Critical Pitfalls to Avoid

• Do not miss the prodromal window—abortive therapy effectiveness drops dramatically if not taken immediately at symptom onset 1
• Do not diagnose "luteal phase deficiency" if progesterone is <6 nmol/L—this represents anovulation requiring investigation for PCOS, not inadequate corpus luteum function 4
• Do not dismiss diarrhea as unrelated—gastrointestinal symptoms commonly worsen during the luteal phase in women with motility disorders due to progesterone's inhibitory effect on GI motility 5, 6
• Do not overlook the temporal pattern—the strict relationship to your menstrual cycle is the key diagnostic feature that distinguishes this from typical CVS and guides treatment toward hormonal suppression 3

Prognosis with Treatment

The case report of catamenial CVS treated with GnRH analog demonstrated complete symptom resolution maintained for 5 years, even after resuming normal menstruation, suggesting that temporary hormonal suppression may provide long-lasting benefit. 3 However, symptom recurrence is possible and may require repeat treatment. 3