9.7 — Reading the Gut: What Your Symptoms Actually Mean

A doctor assessing abdominal symptoms is doing something you can partly do yourself: matching where it hurts, what changed, and what came with it against a map of what lies where. This chapter assembles that map from the whole Part, and it ends with the short list of findings that mean go now.

Most digestive symptoms are benign, self-limiting and explainable, and it is worth saying that first, because the internet does the opposite.

Where it hurts

The abdomen is divided into regions for exactly this purpose (Chapter 4.1), and location is the single most informative feature.

Where	Most likely
Right upper	Gallbladder, liver
Epigastric (upper middle)	Stomach, duodenum, pancreas, heart
Left upper	Stomach, spleen, pancreas
Central	Small intestine, early appendicitis, aorta
Right lower	Appendix, right ovary, caecum
Left lower	Sigmoid colon, left ovary
Suprapubic	Bladder, uterus
Loin, radiating to groin	Kidney or ureteric stone

Two entries in that table deserve underlining.

Epigastric pain can be cardiac. An inferior heart attack (Chapter 7.7) frequently presents as upper abdominal pain with nausea and sweating, and is misattributed to indigestion. Anyone over 40 with new epigastric pain, particularly with sweating, breathlessness or a history of heart disease, gets an ECG.

Central abdominal or back pain in an older person can be an aortic aneurysm (Chapter 7.5), and a pulsatile mass is felt for specifically.

How the pain behaves

The character tells you which structure and what is happening to it.

Colicky pain — coming in waves, building and easing over minutes. This is a hollow tube contracting against an obstruction, and the rhythm reflects peristalsis. Bowel obstruction, gallstones, kidney stones. A person with colic is restless and cannot find a comfortable position.

Constant, sharp, localised pain, worse on any movement — this is peritoneal irritation. The person lies absolutely still, avoids coughing, and often flexes their knees. Perforation, appendicitis with peritonitis, or any inflamed organ touching the abdominal wall lining.

The restless-versus-still distinction is genuinely diagnostic, and it can be made from the doorway before a word is spoken.

Burning — acid. Reflux, ulcer.

Radiating through to the back — pancreas, or an aortic problem. Relieved by leaning forward suggests pancreas (Chapter 9.5).

Referred pain follows the embryological nerve supply, and it explains several patterns that otherwise look random.

Gallbladder pain refers to the right shoulder blade tip, because the diaphragm above it is supplied from C3–C5 (Chapter 6.4). Appendicitis begins centrally and moves (Chapter 4.1). A kidney stone radiates from loin to groin, following the ureter's nerve supply.

What came with it

Vomiting. Its timing and content localise the problem.

Vomiting relieving the pain suggests stomach outlet obstruction. Bilious (green) vomiting means the obstruction is below the bile duct entry. In a newborn this is an emergency (Chapter 4.5). Faeculent vomiting — foul, brown — means a distal small bowel obstruction of some duration. Vomiting blood or coffee grounds — upper gastrointestinal bleeding. Emergency.

Bowel habit.

Absolute constipation with no passage of wind, plus vomiting and distension, is bowel obstruction. Four features together: pain, vomiting, distension, constipation. The order in which they appear tells you the level — vomiting early and distension late means a high obstruction; distension early and vomiting late means a low one.

A persistent change in bowel habit over the age of 50, particularly looser and more frequent, warrants investigation, because that is how colorectal cancer most often announces itself.

Fever points toward infection or inflammation — cholecystitis, diverticulitis, appendicitis, cholangitis.

Jaundice narrows things sharply (Chapter 9.4).

Weight loss that is unintended is the symptom that changes the urgency of everything else.

The simple tests, and what each actually shows

Blood tests.

Full blood count — anaemia points to bleeding or malabsorption; a raised white count points to infection or inflammation.

Liver tests — Chapter 9.4. The pattern matters more than the numbers. ALT and AST raised out of proportion means liver cell damage — hepatitis, drugs, alcohol, fatty liver. Alkaline phosphatase and GGT raised out of proportion means a bile drainage problem — stones, stricture, tumour.

Amylase and lipase — pancreatitis.

Coeliac antibodies — and the person must be eating gluten (Chapter 9.3).

Ferritin and iron studies — iron deficiency in a man or a postmenopausal woman means investigate the gut (Chapter 7.1).

Stool tests.

Faecal calprotectin is one of the most useful tests in gastroenterology and deserves explaining. It is a protein released by neutrophils, so it is raised when there are inflammatory cells in the gut and normal when there are not. It therefore distinguishes inflammatory bowel disease from irritable bowel syndrome — which is exactly the distinction that used to require colonoscopy. A normal calprotectin in a young person with typical IBS symptoms is strong reassurance and avoids an invasive test.

Faecal immunochemical test (FIT) detects human haemoglobin in stool. Used both for population screening and increasingly to triage symptomatic patients, because a negative FIT substantially lowers the probability of colorectal cancer.

Stool culture and toxin testing for infection.

Faecal elastase — low in pancreatic exocrine failure.

Breath tests. The urea breath test for H. pylori (Chapter 9.2), hydrogen breath tests for lactose intolerance and bacterial overgrowth.

Imaging and endoscopy.

Ultrasound — first-line for gallstones, liver and kidneys. No radiation, cheap, and operator-dependent. CT — the workhorse for acute abdominal pain in adults. MRI — for bile ducts (MRCP) and for detailed pelvic and small bowel imaging. Endoscopy — direct view plus biopsy, upper or lower. Capsule endoscopy — a swallowed camera for the small bowel, which is otherwise hard to reach.

The alarm features

These are the findings that change the pathway from "reassure and treat" to "investigate promptly", and they are worth knowing for yourself.

Investigate soon:

• Difficulty swallowing, especially progressive.
• Unintended weight loss.
• Persistent vomiting.
• Iron deficiency anaemia.
• A persistent change in bowel habit over 50.
• Rectal bleeding — usually benign, always worth reporting.
• A palpable abdominal mass.
• New dyspepsia over 55.
• Jaundice.
• A family history of bowel cancer at a young age.

Go to hospital now:

• Vomiting blood, or black tarry stool.
• Sudden severe abdominal pain, particularly if the abdomen is rigid and any movement hurts.
• Abdominal pain with fever and jaundice (Chapter 9.4).
• Abdominal pain with collapse, or with a pulsatile mass.
• Absolute constipation with vomiting and distension.
• Severe pain with a tender irreducible lump in the groin (Chapter 6.4).
• Any abdominal pain in a woman of reproductive age until pregnancy has been excluded (Chapter 4.3).

And one that is easy to miss: abdominal pain in a person with diabetes who is unwell, drowsy or breathing deeply may be diabetic ketoacidosis rather than a surgical problem (Chapter 18.7).

What the gut does well

The Part closes on the same note the respiratory Part did, because the digestive system is genuinely impressive and most of its diseases are manageable.

It handles a hostile job continuously. It processes 30 tonnes of food across a lifetime, maintains a chemical gradient of five pH units across a fraction of a millimetre in the stomach, and hosts 38 trillion bacteria while keeping them out of the bloodstream — using a barrier one cell thick that is completely replaced every three to five days.

It repairs remarkably well. The intestinal lining regenerates fully within days. The liver regrows most of its mass within weeks. Villi flattened by coeliac disease return to normal on a gluten-free diet. Ulcers heal. The gut flora re-establishes.

And the practical list is short, cheap and unglamorous. Fibre from a wide variety of plants feeds the bacteria that feed your colon lining. Adequate fluid. Regular movement, which drives gut motility. Not smoking, which affects reflux, ulcers, Crohn's disease and several gut cancers. Moderate alcohol, since the liver and pancreas take the direct hit. And taking part in bowel cancer screening when it is offered, which is the one intervention on this list that prevents a cancer rather than reducing a risk.

Most digestive symptoms are benign. The alarm list above exists precisely so that the small proportion that are not can be found early, when they are still very treatable.

What Part 10 does next

Everything absorbed has to be balanced by something excreted, and the organ that decides what stays and what goes is astonishingly precise about it. Part 10 covers the kidneys — how they filter 180 litres a day and return 179 of it, how they hold your blood chemistry to tolerances a laboratory would struggle to match, and what dialysis is actually replacing.