Gastric outlet obstruction (GOO) is a condition where a blockage prevents the normal emptying of stomach contents. This obstruction occurs at the stomach’s exit or in the initial part of the small intestine, leading to a buildup of food and fluids and causing various symptoms.
The Mechanics of Gastric Outlet Obstruction
The digestive process begins with food entering the stomach, where it breaks down into a semi-liquid mixture called chyme. This chyme then passes through the pylorus, a valve-like opening at the bottom of the stomach, into the duodenum, the first segment of the small intestine.
GOO occurs when a physical impediment blocks this pathway, specifically in the distal stomach, pyloric channel, or duodenum. This prevents chyme from moving into the small intestine, causing the stomach to enlarge with accumulating food and secretions.
Underlying Causes of Obstruction
The reasons for gastric outlet obstruction can be broadly categorized into benign (non-cancerous) and malignant (cancerous) conditions. Historically, benign causes, particularly peptic ulcer disease, were the most common. However, with advancements in treatment for Helicobacter pylori infection and the widespread use of acid-reducing medications, the prevalence of peptic ulcer disease as a cause of GOO has decreased.
Peptic ulcer disease can cause obstruction through acute inflammation and edema, or chronic scarring and fibrosis, particularly from ulcers in the pyloric channel or first part of the duodenum. Other benign causes include inflammation from conditions like Crohn’s disease or eosinophilic gastroenteritis, strictures from caustic ingestion, and pancreatic disorders such as pancreatitis or pancreatic pseudocysts that compress the duodenum. Rare causes also include bezoars and gallstones that block the pylorus.
Malignant causes now account for a significant proportion, often between 50% and 80%, of gastric outlet obstruction cases. Pancreatic cancer is currently the most common malignancy leading to GOO, as tumors in the pancreas can press on the adjacent duodenum. Gastric cancer, including tumors growing within the stomach, also frequently causes obstruction by directly compressing the pylorus or surrounding tissues. Other cancers that may lead to GOO include duodenal cancer, cholangiocarcinoma, gastrointestinal stromal tumors (GISTs), lymphoma, and metastatic cancers that spread to the region.
Recognizing the Symptoms
Individuals with gastric outlet obstruction experience symptoms due to the stomach’s inability to empty properly. Nausea and vomiting are common, with vomit often containing undigested food without bile, as food cannot move past the blockage into the small intestine.
Upper abdominal pain is another frequent symptom. Patients may also report early satiety. Over time, persistent vomiting can lead to unintended weight loss and dehydration. A dilated stomach may sometimes be observed or felt during a physical examination.
How Gastric Outlet Obstruction is Diagnosed
The diagnostic process for gastric outlet obstruction typically begins with a thorough review of the patient’s medical history and a physical examination. Healthcare providers will inquire about the nature and duration of symptoms, such as vomiting patterns and any weight changes. Initial blood tests may reveal imbalances in electrolytes, such as low potassium, or signs of dehydration.
Imaging studies identify the obstruction’s location and nature. An upper GI series involves drinking a barium solution, visualized on X-rays to reveal narrowing or blockages. Endoscopy involves inserting a thin, flexible tube with a camera into the stomach and duodenum, allowing direct visualization, biopsies to determine the cause (e.g., cancer), and sometimes therapeutic use. CT scans may also assess the obstruction’s extent and identify external compressions or tumors.
Treatment Approaches
Treatment for gastric outlet obstruction is tailored to the underlying cause and the severity of the blockage. Initial management often involves supportive care, such as intravenous fluids to correct dehydration and electrolyte imbalances, and placing a nasogastric tube to decompress the stomach and relieve discomfort. Medical management plays a role, particularly for benign causes like peptic ulcer disease, where proton pump inhibitors can reduce stomach acid and promote healing. Eradication of Helicobacter pylori infection, if present, is also an important step.
Endoscopic interventions offer less invasive options for many patients. Balloon dilation involves inserting a balloon through an endoscope and inflating it to widen the constricted area, which is particularly effective for benign strictures. For malignant obstructions, self-expanding metal stents can be endoscopically placed to create an open passageway, allowing food to pass and improving quality of life, especially for patients with a poor prognosis. Endoscopic ultrasound-guided gastroenterostomy (EUS-GE) is a newer technique that creates a bypass between the stomach and small bowel using a stent, guided by ultrasound.
Surgical options are considered when medical or endoscopic treatments are unsuitable or have failed. Procedures may involve resecting scar tissue or tumors causing the obstruction. A common approach is gastrojejunostomy, which creates a bypass by connecting the stomach directly to the jejunum. The choice between treatments depends on the patient’s overall health, the obstruction’s nature, and the expected long-term outcome.