Blind loop syndrome is a complication of Billroth II gastrectomy and gastroenterostomy or other end-to-end or end-to-side bowel anastomosis consisting of dilatation of a bypassed intestinal loop, that becomes excluded from normal intestinal transit. This can lead to stasis, bacterial population overgrowth, mucosal ulceration, short bowel syndrome, and malabsorption.
Blind loop syndrome patients presents with non-specific symptoms, such as nausea, lack of appetite, dyspepsia, flatulence, abdominal distention and pain, early satiety, diarrhea, steatorrhea, unintentional weight loss eventually leading to cachexia and nutrient deficiencies, such as vitamin B12, leading to megaloblastic anemia  or protein deficiency due to steatorrhea and malabsorption, causing peripheral edema . In children, the physician will notice growth retardation. Although these findings are caused by due to different etiologies, in this case, they are due to the loss of defense mechanisms in the by-passed intestinal loop   and to the decreased absorption surface. A high level of suspicion should be raised in the patients who underwent abdominal surgery, especially gastroenterostomy or Billroth II gastric resection.
Symptoms develop gradually, over a long period of time and also consist of other vitamin deficiency signs, such as blepharitis, glossitis, and cheilosis, neurologic abnormalities: decreased proprioception and deep tendon reflexes  and additional digestive signs, like bilious vomiting , caused by convulsive emptying of the blind loop.
The first step in diagnosing blind loop syndrome is to do an abdominal radiograph, which will show a nonspecific gas collection; this aspect may be absent if the loop is not empty. Barium fluoroscopy may bring additional information in this case, as well as exclude intestinal diverticulosis or strictures. Thus, barium can enter a limited portion of the afferent loop, not enter it at all or enter and then be propelled back into the stomach .
A computer tomography will help observe the anastomosis and an adjacent dilated intestinal loop, that may be filled with feces, leading to a difficult imaging differential diagnosis with small bowel obstruction or abscess . Abdominal computer tomography and computer tomography enterography also provide information about neighboring structures, such as the pancreas.
Hydrogen breath test is used to measure the level of exhaled hydrogen; if high, this suggests carbohydrate maldigestion and bacterial overgrowth syndrome, a complication of the blind loop. This can also be diagnosed using D-xylose breath test, that measures the exhaled carbon dioxide level.
Steatorrhea dictates the need for a quantitative fecal test, also an indicator of small intestinal bacterial overgrowth syndrome, chronic pancreatitis or short bowel syndrome. Bile acid breath test can also be performed, in order to identify bile dysfunction. If small intestinal bacterial overpopulation is still uncertain at this point, a small intestinal aspirate and culture need to be performed, having in mind that this is the diagnosis gold standard in this instance.
Absorption of various nutrients being impaired in blind loop syndrome, various malabsorption diagnosis techniques has been developed. Co60-tagged vitamin B12 urinary and fecal excretion and hepatic uptake are examples of these methods   . If urinary vitamin B12 is diminished, the test is repeated after intrinsic factor is administered. If urinary excretion becomes normal, the diagnosis is pernicious anemia, probably caused by gastric atrophy, and blind loop syndrome is disproved. Gastric fluid analysis and gastric biopsy may also be helpful in certain cases.