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This is the complete lecture note for MED404 Gastroenterology I. You can read it online below, open it in the full viewer, or download the PDF for offline study. It pairs with the course's video lectures, so you can read and watch together.
Course code: MED 404 Course title: Gastroenterology I Course credit load: 2 Units Series 1: Evaluation of Gastrointestinal Symptoms • Part 1.1: Approach to Abdominal Pain o Sub Part 1.1.1: Mechanisms and classification of abdominal pain o Sub Part 1.1.2: History taking and physical examination o Sub Part 1.1.3: Investigation of abdominal pain • Part 1.2: Approach to Gastrointestinal Bleeding o Sub Part 1.2.1: Upper gastrointestinal haemorrhage o Sub Part 1.2.2: Lower gastrointestinal bleeding o Sub Part 1.2.3: Investigation and initial management • Part 1.3: Approach to Jaundice o Sub Part 1.3.1: Classification and pathophysiology of jaundice o Sub Part 1.3.2: Clinical assessment of the jaundiced patient o Sub Part 1.3.3: Investigation and differential diagnosis • Part 1.4: Approach to Weight Loss and Abdominal Swelling o Sub Part 1.4.1: Evaluation of unintentional weight loss o Sub Part 1.4.2: Abdominal swelling and ascites o Sub Part 1.4.3: Investigation of weight loss and abdominal swelling
Introduction The ability to evaluate gastrointestinal symptoms accurately is one of the most important clinical skills in internal medicine and gastroenterology. In Nigeria, gastrointestinal complaints account for a significant proportion of outpatient consultations and emergency presentations. Conditions ranging from peptic ulcer disease and viral hepatitis to intestinal obstruction and colorectal malignancy often begin with the same cluster of symptoms, making a disciplined, systematic approach essential for reaching the correct diagnosis without delay. The aim of this Series is to equip you with a structured clinical framework for evaluating the four major gastrointestinal symptom complexes encountered in practice. We shall commence this Series by examining abdominal pain, exploring its mechanisms, structured history, physical examination, and investigation pathway. Next, we will explore gastrointestinal bleeding, distinguishing upper from lower GI sources and describing the immediate management. Moving on, we will consider the clinical approach to jaundice, from its pathophysiological classification to the investigation pathway. Finally, we will conclude by addressing unintentional weight loss and abdominal swelling, including the assessment and investigation of ascites. Series Learning Outcomes Upon completing this Series, you should be able to: • SLO 1.1: describe the mechanisms and classification of abdominal pain, • SLO 1.2: conduct a systematic clinical assessment of a patient with abdominal pain, • SLO 1.3: distinguish between upper and lower gastrointestinal bleeding and describe the clinical features of each, • SLO 1.4: outline the investigation and initial management of gastrointestinal bleeding, • SLO 1.5: classify jaundice according to its pathophysiological mechanism, • SLO 1.6: describe the clinical assessment and investigation of the jaundiced patient,
• SLO 1.7: define clinically significant unintentional weight loss and identify its gastrointestinal causes in Nigeria, and • SLO 1.8: describe the clinical approach to abdominal swelling and ascites including the serum-ascites albumin gradient. 1.1 Approach to Abdominal Pain 1.1.1 Mechanisms and classification of abdominal pain Abdominal pain arises through three distinct mechanisms. Visceral pain is produced by distension, spasm, or ischaemia of a hollow viscus such as the bowel, gallbladder, or ureter. Because visceral afferent nerve fibres from both sides of the body converge at the same spinal level, this pain is poorly localised and felt diffusely in the midline, described as dull, cramping, or colicky in character. Parietal pain arises from direct irritation of the parietal peritoneum, which is richly supplied by somatic nerve fibres, making it sharp, well localised, and worsened by movement or coughing. Referred pain is perceived at a site distant from the diseased organ due to shared spinal nerve roots, as in right shoulder tip pain from diaphragmatic irritation in biliary disease. Abdominal pain is further classified by onset and location. Sudden onset suggests a surgical emergency such as hollow viscus perforation or mesenteric vascular occlusion, while gradual onset suggests an inflammatory or obstructive process. Location provides important diagnostic clues: right hypochondrial pain points to biliary or hepatic pathology, epigastric pain to peptic ulcer disease or pancreatitis, periumbilical pain migrating to the right iliac fossa is the classic evolution of appendicitis, and left iliac fossa pain suggests colonic disease such as diverticulitis or colitis. ________ pain is poorly localised and felt in the midline because visceral afferent fibres are bilateral, while ________ pain is sharp and well localised because the parietal peritoneum is supplied by somatic nerve fibres. 1.1.2 History taking and physical examination
A thorough history of abdominal pain follows the SOCRATES framework: Site (where the pain is worst), Onset (sudden suggests perforation or vascular catastrophe; gradual suggests inflammation), Character (colicky or constant), Radiation (to the back suggesting pancreatitis or aortic aneurysm; to the right shoulder suggesting biliary disease), Associations (nausea, vomiting, fever, change in bowel habit, jaundice, urinary symptoms), Timing (continuous or intermittent), Exacerbating and relieving factors, and Severity. The past medical and drug history must include previous abdominal surgery, peptic ulcer disease, inflammatory bowel disease, sickle cell disease, and use of non-steroidal anti-inflammatory drugs. In women of reproductive age, the gynaecological history is essential to exclude ectopic pregnancy and pelvic inflammatory disease. Physical examination begins with general inspection for pallor, jaundice, and diaphoresis, followed by vital signs. Tachycardia, hypotension, and fever indicate severity and the need for urgent intervention. Abdominal palpation identifies guarding (voluntary resistance), involuntary rigidity (board-like firmness indicating generalised peritonitis), and rebound tenderness (pain on sudden release of pressure indicating peritoneal irritation). Specific signs include Murphy's sign (arrest of inspiration on right hypochondrial palpation, indicating cholecystitis), Rovsing's sign (right iliac fossa pain on left iliac fossa pressure, indicating appendicitis), and the succussion splash of intestinal obstruction. A digital rectal examination is mandatory in all patients with acute abdominal pain. In the SOCRATES framework, radiation of abdominal pain to the ________ suggests pancreatitis, while radiation to the right ________ tip suggests biliary disease. 1.1.3 Investigation of abdominal pain First-line investigations include a full blood count (leucocytosis in infection or inflammation), C-reactive protein and erythrocyte sedimentation rate, serum amylase and lipase (elevated in pancreatitis), liver function tests, urine dipstick, and a pregnancy test in all women of reproductive age. These investigations rapidly narrow the differential diagnosis and guide further imaging.
Imaging begins with a plain abdominal X-ray, which identifies dilated bowel in obstruction and, on an erect chest X-ray, free gas under the diaphragm in perforation. Abdominal ultrasound is the first-line modality for hepatobiliary and renal pathology. CT of the abdomen and pelvis is the most sensitive investigation for most acute abdominal emergencies and is used when the diagnosis remains uncertain after initial assessment. Free gas under the right hemidiaphragm on an erect chest X-ray indicates bowel ________. Serum ________ and lipase are the key biochemical markers for pancreatitis. Figure 1.1: Regional differential diagnosis of abdominal pain Pilot questions 1.1 1. Describe the three mechanisms of abdominal pain. (Linked to SLO 1.1) 2. State two features that distinguish parietal pain from visceral pain. (Linked to SLO 1.1)
3. Describe four components of the SOCRATES framework as applied to abdominal pain. (Linked to SLO 1.2) 4. State the significance of Murphy's sign and Rovsing's sign. (Linked to SLO 1.2) 5. Name two radiological findings that indicate a surgical emergency in acute abdominal pain. (Linked to SLO 1.2) 1.2 Approach to Gastrointestinal Bleeding 1.2.1 Upper gastrointestinal haemorrhage Upper gastrointestinal (UGI) haemorrhage is defined as bleeding from a source proximal to the ligament of Treitz. It presents as haematemesis, which is the vomiting of blood that is bright red when bleeding is active or coffee-ground when blood has been partially digested, or as melaena, which is the passage of black, tarry, foul-smelling stools from degradation of blood during GI transit. The most common causes in Nigeria are peptic ulcer disease (the most frequent cause overall), oesophageal varices from portal hypertension in liver cirrhosis (the most life-threatening cause), Mallory-Weiss tears, oesophagitis, and gastric malignancy. The clinical assessment must rapidly identify haemodynamic compromise: a heart rate above 100 beats per minute, systolic blood pressure below 100 mmHg, and postural dizziness indicate significant blood loss requiring immediate resuscitation. The Glasgow-Blatchford score, using blood urea, haemoglobin, blood pressure, pulse rate, and clinical features, stratifies risk and guides the urgency of endoscopy. A markedly elevated blood urea to creatinine ratio is a biochemical clue to upper GI bleeding, as digested blood is absorbed and converted to urea. Upper GI haemorrhage presents as ________ or melaena. The most life-threatening cause in a patient with chronic liver disease is bleeding from oesophageal ________. 1.2.2 Lower gastrointestinal bleeding
Lower gastrointestinal (LGI) bleeding originates distal to the ligament of Treitz and presents as haematochezia, the passage of bright red or maroon blood per rectum. In young adults in Nigeria, the most common causes are haemorrhoids (the most common cause overall), anal fissures, and infectious colitis from bacterial dysentery or amoebic colitis. In patients above 40 years, colorectal carcinoma must always be excluded, alongside diverticular disease and angiodysplasia. Blood coating the outside of the stool suggests an anal or low rectal source, whereas blood mixed within the stool suggests a colonic source. Massive upper GI bleeding may also present as haematochezia when colonic transit is rapid, so haemodynamic status and the urea to creatinine ratio help distinguish lower from upper GI bleeding
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