I have been performing gastric resections for many years. For many patients this operation is a new life after obesity: weight loss, improvement of diabetes, arterial hypertension, and joint pain. But resection is not a “magic pill”: it is a surgical intervention with specific complications, some of which are rare but potentially serious. My goal is to explain the real side effects in plain language so that you can make an informed decision and know what to watch for after the operation.

Key complications — short and to the point

Below is a table of the main side effects, their approximate frequency, when they usually occur, how they present, and what my colleagues and I typically do about them.

Side effect	Frequency (approx.)	When it usually occurs	Signs / symptoms	What to do / treatment / prevention
Staple-line leak (staple-line leak)	~0.7–3% (on average ≈1–3%).	Early — within the first 1–14 days; late/occult — weeks/months after surgery.	Pain in the upper abdomen, fever, tachycardia, sometimes peritonitis; with a contained abscess — systemic toxicity.	Urgent evaluation (CT with oral and IV contrast, contrast swallow), antibiotics, nasogastric decompression/percutaneous drainage, endoscopic stents/endoscopic vacuum therapy (E-VAC) or surgical washout — the decision is individualized. High operative volume and meticulous technique reduce risk.
Gastroesophageal reflux disease (GERD)	Up to ~25–35% (varies across series).	Often develops months to years after surgery.	Heartburn, regurgitation of acidic content, erosive esophagitis; rarely — Barrett’s esophagus with chronic reflux.	Conservative: proton pump inhibitors (omeprazole etc.), lifestyle modification; for persistent or progressive reflux — consider revisional bypass (conversion to RYGB) or other surgical/endoscopic options. Endoscopic surveillance is required for persistent symptoms.
Stricture (tube stenosis) / pyloric stenosis	Uncommon — fractions of a percent to a few percent.	From several weeks to months.	Nausea, vomiting, difficulty with oral intake, delayed passage of liquids/food.	Diagnosis — contrast radiography / EGD (esophagogastroduodenoscopy); endoscopic balloon dilation is often effective; occasionally repeat surgery is necessary.
Nutritional deficiencies (B12, iron, vitamin D, calcium, folate, etc.)	Common in the long term — varies by nutrient (declines in B12/Fe/vitamin D are frequently observed).	Months to years (cumulative effect).	Anemia, fatigue, paresthesias (with B12 deficiency), osteopenic changes, muscle weakness.	Planned lifelong monitoring — labs 1–2 times per year, prescription of multivitamins, targeted supplements as needed (B12 — parenteral or high-dose oral; iron — oral or IV). Adherence to dietary guidance from a nutritionist is important.
Dumping syndrome (rapid gastric emptying)	After sleeve gastrectomy (SG) — more common than in the general population but less common than after RYGB; some studies report ≈10–20% (criteria-dependent).	Early — minutes after eating; late — 1–3 hours after a meal (reactive hypoglycemia).	Nausea, diarrhea, weakness, dizziness, sweating, tachycardia; late — tremor/sweating due to hypoglycemia.	Dietary modifications (small frequent meals, avoid simple sugars), medications when indicated; in rare refractory cases — surgical options may be considered.
Bleeding (intraoperative / early postoperative)	Low frequency but requires attention.	Within the first days after surgery	Pallor, tachycardia, drop in hemoglobin, pain.	Hemodynamic stabilization, re-operation if needed; prophylaxis includes meticulous hemostasis of vessels/staples and correction of coagulopathies before surgery.
Thromboembolism / wound infection	Overall somatic risk — reduced by prophylaxis.	Early / in the postoperative period	Shortness of breath, leg pain, redness/discharge from the wound.	Thromboprophylaxis (compression stockings and heparin per protocol), early mobilization, antibiotics for wound infection.
Weight regain / failure to achieve goals	Depends on patient behavior and operation type; up to 15–30% at 5–10 years may experience partial weight regain.	Years after surgery	Gradual increase in body weight	Support from a dietitian, lifestyle revision; in some cases — endoscopic or surgical revisional procedures.
Psychological / behavioral problems	Significant prevalence (depression, food-to-substance substitution — “addiction transfer”).	Any time	Mood swings, dietary lapses, problems with adjustment	Psychological support before and after surgery, support groups, psychiatric treatment if needed.

(Note: the table shows approximate ranges; exact figures vary between studies and depend on sample size, center experience, and follow-up duration.)

What particularly concerns me as a surgeon (and why)

Leak — the “nightmare” of the early period. Although the frequency is relatively low (a few percent), a leak can rapidly progress to an abscess or generalized peritonitis. We do everything to prevent it: meticulous technique when creating the sleeve, assessment of wall perfusion, careful handling of thick fat, and intraoperative leak testing. At the first signs we do not “watch and wait” — we investigate promptly (CT scan, labs).
Chronic reflux after sleeve. This is something patients sometimes underestimate: “I lost weight — I don’t want pills anymore,” — but within 1–3 years a portion of patients develop persistent reflux, some develop erosive esophagitis and even premalignant changes (Barrett’s). For refractory reflux we discuss revisional surgery (for example, conversion to Roux-en-Y gastric bypass) because medical therapy does not always resolve the problem.
Nutritional loss — the “silent” danger. A patient may look well, but over years iron, B12, and vitamin D stores can be depleted, resulting in anemia, paresthesias, and bone fragility. That is why I insist on lifelong laboratory monitoring and adherence to vitamin supplementation protocols.

Practical advice for the patient (from the surgeon)

Before the operation: complete evaluation (labs, EGD/esophagogastroduodenoscopy, H. pylori testing when indicated), consult with a dietitian and a psychologist. Better preparation leads to lower complication rates.
The first month after surgery: if temperature >38°C, severe pain, fever, or persistent vomiting — contact your surgeon immediately. Early problems are easier and faster to treat.
Long-term: 1–2 times per year — blood tests (Hb, ferritin, B12, vitamin D, calcium), follow-up with a dietitian; for persistent heartburn — endoscopy.
Managing GERD symptoms: try PPIs, dietary changes; if ineffective — we will discuss surgical correction.

Finally — honestly about risks vs benefits

I tell my patients honestly: yes, there is a risk of complications — from early (leak, bleeding) to long-term (reflux, nutrient deficiencies, weight regain). But for the vast majority of people the benefits outweigh the risks: significant and sustained weight loss, remission of type 2 diabetes, improvement in sleep, blood pressure, and quality of life. The most important factor is your attitude and willingness to commit to lifelong follow-up and lifestyle changes.