Abdominal pain following bariatric surgery is common. In most cases it is benign and self-limiting. However, it may also represent a serious, time-critical complication requiring urgent surgical assessment.
For GPs across Dunedin, Otago, Southland, Queenstown, Wanaka and Invercargill who refer to Southern Weight Loss, the challenge is clear:
When should abdominal pain be managed conservatively, and when is same-day referral required?
This guide provides a practical, New Zealand-focused framework for primary care.
Why This Matters in the Southern Region
We increasingly see patients who:
- Have not undergone bariatric surgery locally at Mercy Hospital Dunedin
- Had surgery elsewhere in New Zealand
- Have travelled overseas for bariatric procedures
In patients with unclear operative details or altered anatomy, clinical risk increases. Delayed diagnosis of complications such as internal hernia or leak can result in bowel ischemia, sepsis, and avoidable morbidity.
The guiding principle:
Pain that is severe, progressive, persistent, or associated with systemic features warrants urgent surgical review.
Common (usually benign) causes of abdominal pain
Most post-bariatric abdominal discomfort seen in general practice relates to functional or dietary issues.
These include:
- Dietary intolerance or rapid eating
- Common after sleeve gastrectomy or gastric bypass
- Often post-prandial
- Improves with slower eating and portion control
- Gas and constipation
- Frequently related to reduced fibre intake
- Can cause cramping or bloating
- Mild Dumping syndrome
- Occurs after high-sugar meals
- Associated with palpitations, sweating, and loose stools
- Self-limiting with dietary modification
- Biliary colic during rapid weight loss
- Occurs commonly within first 6–12 months
- Intermittent right upper quadrant pain
These presentations are typically:
- Mild to moderate
- Non-progressive
- Not associated with systemic illness
- Responsive to conservative management
Red-flag symptoms: same-day referral required
The following clinical features warrant urgent referral to emergency services or direct surgical contact with Southern Weight Loss.
1. Severe or escalating abdominal pain
- Pain out of proportion to examination findings
- Rapid progression over hours
- Pain waking the patient from sleep
Concern:
- Internal hernia
- Small bowel obstruction
- Anastomotic leak
- Bowel ischemia
Internal hernia is particularly important in gastric bypass patients and can present months or years post-operatively.
2. Persistent vomiting or inability to tolerate fluids
- Vomiting beyond 24 hours
- Signs of dehydration
- Electrolyte disturbance
Concern:
- Obstruction
- Stricture
- Volvulus
- Internal hernia
Inability to tolerate fluids in a post-bariatric patient should never be observed expectantly.
3. Tachycardia, fever or hypotension
- Resting heart rate >100 bpm
- Fever
- Unexplained systemic upset
Concern:
- Anastomotic leak
- Sepsis
- Perforation
Tachycardia may precede overt abdominal signs. A normal abdominal exam does not exclude serious pathology.
4. Upper abdominal pain with GI bleeding or anaemia
- Haematemesis
- Melaena
- Iron-deficiency anaemia
Concern:
- Marginal ulcer
- Staple line bleeding
- Anastomotic erosion
NSAID exposure is a common precipitating factor.
5. Post-prandial pain with progressive food intolerance
- New pain after eating
- Increasing difficulty tolerating solids
- Weight loss plateau or failure
Concern:
- Anastomotic stricture
- Ulceration
- Sleeve stenosis
6. Colicky pain months to years after Bypass
- Intermittent cramping
- Associated nausea
- Self-resolving episodes
Concern:
- Internal hernia
These patients may present multiple times before diagnosis. CT imaging is often required even if examination is unremarkable.
7. Right upper quadrant pain with systemic features
- Fever
- Jaundice
- Elevated inflammatory markers
Concern:
- Acute cholecystitis
- Choledocholithiasis
- Pancreatitis
Gallstone disease is common during rapid weight loss.
When GP management is appropriate
Short-term conservative management may be reasonable if symptoms are:
- Mild
- Improving
- Not associated with systemic features
- Clearly linked to dietary triggers
Examples:
- Mild reflux
- Constipation-related discomfort
- Intermittent cramping
Patients must be advised to re-present urgently if symptoms worsen or fail to settle within 24–48 hours.
Practical investigation guidance for GPs
DO NOT RELY on a “Normal” abdominal exam
Serious pathology, particularly internal hernia, may present with minimal tenderness.
Clinical deterioration may precede peritonism.
First-line imaging
If red flags are present:
CT abdomen with oral and IV contrast is the investigation of choice.
Ultrasound is appropriate for suspected gallbladder pathology but does not exclude internal hernia or obstruction.
Medication caution
Avoid NSAIDs in post-bariatric patients unless anatomy is clearly known.
Marginal ulcer risk is significantly increased after gastric bypass.
Key complications by procedure type
Sleeve Gastrectomy
- Leak (early post-op)
- Stricture
- Reflux-related pain
One Anastomosis Gastric Bypass
- Internal hernia
- Marginal ulcer
- Anastomotic stricture
- Biliary reflux
Understanding the surgical anatomy is critical. If uncertain, early specialist contact is advised.
Why early referral matters
Delayed diagnosis in post-bariatric patients can lead to:
- Bowel ischemia
- Perforation
- Sepsis
- Avoidable laparotomy
- Increased morbidity
Early CT imaging and specialist review protect both patient and clinician.
When in doubt: refer
For GPs across:
- Dunedin
- Otago
- Southland
- Queenstown
- Wanaka
- Invercargill
- Oamaru
Southern Weight Loss provides urgent advice and shared care support.
Same-day discussion is encouraged when:
- Symptoms are atypical
- Anatomy is unclear
- Overseas surgery was performed
- There is clinical uncertainty
Key take-home message for Primary care
Abdominal pain after bariatric surgery is common, but serious complications are uncommon and time-critical.
Same-day referral is warranted when pain is:
- Severe
- Progressive
- Associated with vomiting
- Accompanied by tachycardia or systemic features
- Unexplained
Do not delay imaging or referral based on a reassuring abdominal exam.
Supporting GPs across the Southern region
Southern Weight Loss, led by Mark Grant (Upper GI and Bariatric Surgeon), provides:
- Bariatric surgery in Dunedin (Mercy Hospital)
- Ongoing shared care with local GPs
- Urgent post-operative assessment pathways
- Long-term nutritional monitoring support
We welcome early communication and collaborative management.
This article is intended as a clinical guide for healthcare professionals. Individual patient assessment and specialist consultation remain essential.
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