With an estimated 300,000 admissions annually, acute upper GI bleeding (UGIB) is one of the most common medical emergencies [7]. It is defined as the presence of melena, hematemesis, or blood in the nasogastric (NG) aspirate. Studies have shown improved outcomes of UGIBs in critically ill patients with hemodynamic instability or continuing transfusion requirements, if they are managed endoscopically [8, 9]. The distinction between nonvariceal (peptic ulcer, esophagitis, Mallory-Weiss-tear, angiodysplasia, etc.) and variceal lesions (esophageal or gastric varices) is made endoscopically, allowing for targeted therapy [10, 11]. Furthermore, endoscopic stigmata help to prognosticate risk of rebleeding in peptic ulcers, occasionally revealing lesions that require surgical or radiologic intervention [12].

Foreign body ingestions (FBI) occur commonly. They can be divided into two groups: food impactions and caustic ingestion. Food impactions constitute the majority of FBI. Although most will pass spontaneously, EGD should always be performed to look for the underlying cause of obstruction (strictures, rings, etc.). Endoscopic removal of the food bolus is necessary in 10% to 20% of cases, and 1% of patients will ultimately require surgery [13]. Although caustic ingestions only constitute a small number of FBI, they are frequently life-threatening, especially when they occur intentionally in adults. Endoscopy is safe and should be performed for prognostication and triage [14].

Enteral nutrition improves outcomes in critically ill patients and is preferred over parenteral nutrition in patients with a functional GI tract [15]. Although naso- or oroenteric feeding tubes may be used for short-term enteral nutrition, these tubes are felt to carry a higher risk of aspiration, displacement, and sinus infections than endoscopically placed percutaneous tubes. Percutaneous endoscopic gastrostomy (PEG), jejunal extension through a PEG (PEG-J), or direct endoscopic jejunostomy (D-PEJ) [16] are appropriate for many patients in the ICU. They are especially useful in patients with a reversible disease process, likely to require more than 4 weeks of artificial nutrition (e.g., neurologic injury, tracheostomy, neoplasms of the upper aerodigestive tract, etc.) [17]. PEG-J and D-PEJ tubes are appropriate for patients with severe gastroesophageal reflux, gastroparesis, or repeated feeding-related aspiration. Endoscopic gastrostomies or jejunostomies may also be indicated for decompression in patients with GI obstruction [18]. Although this is a technically simple procedure that can be performed at the bedside under conscious sedation, its risks and benefits should always be weighed carefully [19].

Acute lower GI bleeding (LGIB) is defined as bleeding from a source distal to the ligament of Treitz for less than 3 days and is predominantly a disease of the elderly [30]. Common causes are diverticular bleeding, ischemic colitis, and vascular abnormalities. However, as many as 11% of patients initially suspected to have a LGIB are ultimately found to have an UGIB [31]. Therefore, UGIB sources should always be considered first in patients with LGIB. Once an upper GI source has been excluded, colonoscopy should be performed. Although urgent colonoscopy within 24 to 48 hours has shown to decrease the length of hospital stay [32, 33] and endoscopic intervention is
often successful, 80% to 85% of LGIBs stop spontaneously [34]. If the bleeding is severe or a source cannot be identified at colonoscopy, a technetium (TC) 99m red blood cell scan with or without angiography should be considered [35, 36].

Acute colonic obstruction is considered a medical emergency. Imaging studies (abdominal plain films, computed tomography [CT] scan) are needed to differentiate “true” mechanical obstruction from acute colonic pseudoobstruction, because these entities are managed differently.