Liver

The liver arises from the foregut-midgut junction. It is contained in the Glisson capsule, and the falciform ligament attaches the liver to the anterior abdominal wall. Hepatocytes perform approximately 500 functions. Chronic hepatitis C, alcoholic liver disease, and nonalcoholic steatohepatitis may cause cirrhosis and give rise to liver failure and potentially HCC. MRI, CT, and US are helpful for determining the extent of cirrhosis and detecting ascites, tumors, and blood flow. Fifty percent to 80% of the liver can be resected if the remainder functions well. Liver resections may bleed, leak bile, or lead to infection.

Jejunum and Ileum

During development, there is physiologic herniation of the midgut into the umbilical cord, and it then slips back in with a counterclockwise rotation. Jejunum and ileum occupy the mid abdomen and pelvis. The jejunum is involved in calcium and magnesium absorption. The ileum contains lymphoid tissue at the antimesenteric border. Small bowel infections present with a range of symptoms from diarrhea to severe dehydration to sepsis. Suspected SBO can be evaluated with plain radiography, upper GI studies, or CT. The treatment of SBO is initially nonoperative. Paralytic ileus occurs in many patients after abdominal surgery and is treated with IV fluids, nothing by mouth, and electrolyte replacement.

Gallbladder

The endodermal diverticulum of the caudal foregut develops into the GB. The GB lies between liver segments 4B and 5 and is supplied by the cystic artery. Cholecystokinin and vagal stimulation result in GB contraction, delivering bile (synthesized in the liver) into the duodenum. More than 80% of gallstones (cholelithiasis) are of the cholesterol type. Porcelain GBs can be seen on plain radiographs. Unless GB cancer is suspected preoperatively, or dense adhesions are likely, laparoscopic cholecystectomy is the operation of choice. Injury to the CBD (0.5%), duodenum, and liver parenchyma is uncommon but is a serious complication.

Esophagus

The esophagus is a hollow muscular tube approximately 25 cm in length, extending from the cricopharyngeus muscle to the gastroesophageal junction at the gastric cardia. It is the only organ that uses peristalsis. Achalasia is defined as failure of lower esophageal sphincter relaxation with concurrent esophageal aperistalsis. Esophageal manometry is the standard for diagnosing achalasia and DES. Achalasia is managed surgically with a Heller myotomy. Esophageal surgery may result in an iatrogenic perforation, thoracic duct injury, or anastomotic leak.

Trauma Assessment and Surgery

When the patient arrives in the emergency department, the primary survey should be for ABCDE: A, airway; B, breathing; C, circulation; D, disability; and E, exposure. Normothermia is ideal. Check vital signs often. CXR and pelvic radiographs may show evidence of fractures, bleeding, or perforation. If chin lift, jaw thrust, or endotracheal intubation are unsuccessful in establishing an airway, cricothyrotomy is indicated to provide an adequate airway.

Stomach

The stomach develops during the fifth week of gestation from the dilated caudal portion of the foregut. The gastric cardia is just distal to the gastroesophageal junction, the fundus is the upper curvature to the left of the cardia, the body is the central region between the fundus and antrum, and the antrum tapers into the pylorus. Gastric parietal cells secrete hydrochloric acid and intrinsic factor, chief cells secrete pepsinogen, and G cells secrete gastrin. PUD is the most common cause of massive UGI bleeding. Although a UGI series can be used for diagnosis of gastric lesions, some are indistinguishable from benign peptic ulcers. Possible complications of gastric surgery include bleeding, anastomotic leak or stricture, or reflux esophagitis.

Rectum

The rectum develops from endoderm, emerging from the distal tip of the hindgut. The rectum measures 12 to 15 cm. Resting rectal pressure is approximately 10 mm Hg. Internal hemorrhoids cause painless bright-red bleeding. Surgeons evaluate the rectum mainly by performing a digital rectal examination, anoscopy, endorectal US, and MRI to determine the extent of disease. The choice between rubber band ligation and excisional hemorrhoidectomy depends on the location (internal vs external) and degree of internal hemorrhoids. Complications from excisional hemorrhoidectomy may include bleeding, urinary retention, and severe pain.

Parathyroid Glands

The parathyroid glands develop from the endoderm: the superior glands from the fourth pharyngeal pouch, and the inferior glands from the third pharyngeal pouch. Parathyroid glands are usually found on the posterior surface of the thyroid gland. Chief cells secrete PTH, which has a half-life of 3 to 6 minutes. Primary HPT is most often asymptomatic and serendipitously found when the serum calcium value is increased on routine testing. The parathyroid glands can be evaluated with US, CT, MRI, or sestamibi scanning. Cervical exploration for primary HPT involves resection of a solitary adenoma in approximately 85% of patients. Injury to the RLN and superior laryngeal nerve does occur.

Pancreas

The pancreas forms from the dorsal and ventral endodermal buds, which develop at the foregut-midgut junction. The head of the pancreas lies in the duodenal C-loop, anterior to the IVC and left renal vein. Islets of Langerhans carry out the endocrine function of the pancreas. Acute pancreatitis is caused by gallstones, alcohol, and trauma. CT with an IV contrast agent may be used to diagnose pancreatitis, pancreatic cancer, or complications after pancreatic surgery. Most patients with acute pancreatitis are managed conservatively. Pancreatic leaks occur in approximately 20% of operations on the pancreas.

Colon

The colon is made up of the midgut which includes the proximal two-thirds of the transverse colon, and the hindgut, which includes the distal one-third of the transverse colon. The ileocecal junction to the anus is a distance of 1.5 m. Digested food (chyme) passes into the colon and is converted to feces by bacteria. The differential diagnosis of colonic masses includes cancer, carcinoid, lipoma, diverticular disease, ulcerative colitis, polyps, and Crohn disease. Treatment of colorectal cancer and symptomatic inflammatory colon disease usually involves wide surgical resection. Complications after surgery may include postoperative bleeding, leakage, and ileus.