Overview
This lecture covers how to choose imaging for abdominal pain, how abdominal anatomy maps onto radiological findings, and how colorectal cancer is staged with imaging. The first half compares the four modalities (CT, ultrasound, MRI, plain X-ray) by their pros and cons; the second half works through ten clinical vignettes of abdominal pain, pairing each presentation with its diagnosis, the appropriate imaging and the relevant anatomy.
Stated lecture outcomes
- Learn appropriate imaging for abdominal pain.
- Correlate anatomy with radiology findings.
- Imaging of colorectal cancer staging.
- Cases of patients with abdominal pain.
Cases are based on upcoming modules, and each is worked through as: appropriate imaging, discussion of the imaging findings, and the relevant anatomy.
Choosing a modality for abdominal pain
Four modalities are compared. The recurring slide shows an axial CT of the upper abdomen, an ultrasound being performed, a labelled coronal abdominal anatomy image and a plain abdominal X-ray (AXR).
CT
- Pros: fast; great resolution; available.
- Cons: radiation; thin patients.
Ultrasound
- Pros: real time imaging; no radiation; accessible.
- Cons: operator dependant; not good with obese patients. The lecture makes the obesity point with a cartoon in which the sonographer tells the patient “I’m sorry to say all your visceral organs are missing” and the patient replies “I think you are rubbing the pillow”.
MRI
- Pros: excellent detail; identification of small lesions; characterisation.
- Cons: expensive; slow; sensitive to movement.
X-ray (AXR)
- Pros: cheap; fast; accessible.
- Cons: radiation; inaccurate; rarely changes management.
Anatomy to recognise on abdominal imaging
- Axial CT upper abdomen: liver, spleen, kidneys.
- Coronal abdominal anatomy (MRI): liver, spleen, kidneys, psoas, iliacus, gluteus medius, bladder, prostate.
- AXR: gastric air bubble, splenic flexure of the large bowel, spleen, liver, right and left kidney, psoas muscles, bladder.
- Urinary tract (anterior view): inferior vena cava, aorta, adrenal gland, kidney, renal artery, renal vein, ureter, bladder, urethra.
- Colon: caecum, appendix, ascending colon, descending colon, rectum, anus, with peristaltic waves transmitted by intrinsic nerves.
- Biliary tree: cystic duct, hepatic duct, gallbladder, common bile duct, pancreatic duct, duodenum.
- Female pelvis (sagittal): round ligament, uterus, peritoneum, urinary bladder, pubic symphysis, urethra, clitoris, prepuce, labium minus, labium majus.
- Retroperitoneal fascial planes on axial CT: posterior peritoneum, anterior renal fascia, posterior renal fascia, lateroconal fascia, transversalis fascia, bounding the anterior pararenal space, perirenal space and posterior pararenal space.
- Abdominal aorta and branches: phrenic artery, celiac trunk (left gastric artery, common hepatic artery, splenic artery), suprarenal, right and left renal arteries, gonadal, superior mesenteric artery, inferior mesenteric artery, right and left common iliac arteries, right external iliac artery, left internal iliac artery.
- Splenic vasculature: splenic artery and vein, short gastric arteries, left gastro-epiploic artery, with the pancreas and stomach adjacent.
- Femoral access anatomy for angiography: inguinal triangle, common femoral artery, femoral artery bifurcation, inferior epigastric artery, femoral head, access sheath.
Case 1: renal colic
Presentation: 30-year-old woman, sudden onset severe pain in the right lumbar region, came on overnight and worsening, sharp spasms lasting about 10 minutes at a time, slightly nauseated but no vomiting, cannot lie still for examination. Temp 36.0, pulse 80, tender on the right side lower down, urine dipstick positive for blood.
Key points:
- The inability to lie still and the colicky 10 minute spasms with haematuria point to renal colic.
- Anatomy reviewed is the urinary tract from kidney to urethra.
- Imaging shown is coronal CT/urogram with an arrow from a dilated collecting system to a normal one, plus axial CT of both kidneys and coronal bone-window pelvic images, illustrating hydronephrosis and obstruction from a renal stone.
Warning
In the rendered slides no explicit stone or labels are visible on the renal colic imaging, and the cross-sectional kidney line drawing at the slide edge is cropped.
Case 2: sigmoid bowel cancer and colorectal staging
Presentation: 75-year-old man with vague central abdominal discomfort “as though something is not quite right”, previously a bit constipated with occasional diarrhoea, now soft pencil thin stools, lump in the left lower quadrant, looks a bit pale.
Key points:
- Pencil thin stool, altered bowel habit, a left lower quadrant mass and pallor (anaemia) together indicate a sigmoid tumour.
- The colon diagram circles the caecum/appendix area and the rectosigmoid area, the site of the described lesion.
- CT findings: axial, coronal and sagittal pelvic images show a mass or thickened bowel segment in the sigmoid region.
- Imaging is correlated with pathology in a four-panel montage combining mucosal appearance, axial CT at two levels/windows, and a gross or intraoperative photograph of the mass.
- MRI of the pelvis in multiple planes and sequences is used for local (T) staging of the rectosigmoid tumour.
- Distant staging uses PET or PET-CT (coronal whole body) plus CT, with measurements of a nodal lesion and of a vertebral lesion on sagittal spine CT.
T staging by depth of invasion through the bowel wall (layers: submucosa, muscularis propria, serosa):
- T1: invades submucosa.
- T2: invades muscularis propria.
- T3ab and T3cd: through the muscularis propria into/through the serosa, subdivided by depth.
- T4: invades an adjacent organ or structure.
Case 3: ruptured ovarian cyst
Presentation: 25-year-old woman, sudden onset right lower quadrant pain described as “dragging”, came on overnight and worsening, slightly nauseated but no vomiting. Temp 36.0, pulse 80, tender right lower quadrant, urine dipstick negative for blood.
Key points:
- The negative dipstick for blood is the discriminator against renal colic in an otherwise similar overnight-onset presentation.
- Anatomy reviewed is the sagittal female pelvis.
- Imaging is transvaginal/pelvic ultrasound showing uterus and rectum, with free fluid and an adnexal structure consistent with an ovarian cyst.
Case 4: ruptured abdominal aortic aneurysm
Presentation: 75-year-old man playing bowls, sudden very severe abdominal pain, has to sit down, becomes sweaty and pale, “searing” pain going through to his back, ambulance called and he is now on the ground, pale and barely conscious. BP 70 systolic, weak pulse 120, abdomen tender all over.
Pathophysiology, in three stages:
- Initiation: risk factors are genetics, gender, ethnicity, age.
- Progression: risk factors are smoking, infection, trauma, hypertension.
- Rupture.
The mechanistic cycle driving aneurysm formation and rupture: cytokines and inflammation drive oxidative stress and reactive oxygen species, which activate proteases and MMPs; these cause vascular smooth muscle cell apoptosis and extracellular matrix degradation, which in turn increase inflammation and feed the cycle.
Imaging:
- A normal-calibre aorta on axial upper abdominal CT is shown for comparison.
- The retroperitoneal fascial planes and pararenal/perirenal spaces are reviewed, since these are the compartments a ruptured aorta bleeds into.
- The abnormal case shows a large aneurysmal aorta on axial cross-section with surrounding hyperattenuating material (haemorrhage) and kidneys visible bilaterally.
Case 5: gastroenteritis (norovirus)
Presentation: 19-year-old woman with a “funny feeling” in the abdomen, low grade ache for 4 hours, now vomiting persistently, bowel motions becoming loose, nauseous. Temp 37, pulse 90, BP 120/80. Other flat-mates have a similar story. Some epigastric tenderness.
Key points:
- The shared history among flat-mates is the diagnostic clue for infectious gastroenteritis (norovirus).
- CT of the abdomen and pelvis shows relatively unremarkable bowel and mesenteric findings. Labelled structures on the coronal images: liver, stomach, spleen, gallbladder neck, mesentery, ascending colon, small bowel, bladder.
Case 6: gallstones and biliary disease
Presentation: 40-year-old woman, 4 hours of cramping spasms of pain that come and go in the right upper quadrant and go through to her back, worse after a fatty meal, with a similar but milder episode about 6 months ago.
Modality comparison for gallstones (the core teaching point of this case):
| Modality | Stones | Cholecystitis | Other |
|---|---|---|---|
| Abdominal X-ray | Good if calcified, otherwise useless | Cannot tell if there is cholecystitis | |
| CT | Good if calcified, otherwise can be difficult | Not great at cholecystitis | |
| Ultrasound | Great for all gallstones | Great for cholecystitis | Cheap and quick |
| MRI | Great for all gallstones | Great for cholecystitis | Not cheap and not quick |
Findings shown:
- AXR: calcified gallstones in the right upper quadrant, alongside a calcified mesenteric lymph node (the mimic to distinguish).
- CT: multiple rounded calcified/hyperdense structures in the gallbladder.
- Ultrasound of the gallbladder (transverse view): thick wall, free fluid, stones, and absence of echoes posterior to the calculi (“shadowing”), the findings of acute cholecystitis with gallstones.
- MRCP: multiple gallstones causing filling defects in the biliary system.
Clinical discrimination taught by paired images:
- Jaundice plus back/flank pain is presented as the combination pointing to painful gallstone disease.
- Painless jaundice in an older patient is contrasted with it, illustrated by a tumour causing biliary obstruction at the head of the pancreas/distal bile duct, the key differential.
Case 7: small bowel obstruction
Presentation: 42-year-old woman with central abdominal pain in bouts making her bend over and grimace, off her food for over 18 hours but had a normal bowel motion, appendicectomy aged 16, ate an orange the day before the pain, vomited once on arrival at the surgery. Abdomen tender especially centrally with more tenderness on the right, normal rectal examination, absent bowel sounds.
Key points:
- Colicky central pain, vomiting and absent bowel sounds, with previous surgery in the history, indicate small bowel obstruction.
- A normal axial CT of the abdomen is shown first for comparison of bowel calibre.
- Obstructed appearance: multiple dilated radiating small bowel loops, with a strangulated hernia shown as a cause of the obstruction.
- Hernia types listed as causes: indirect inguinal, direct inguinal and femoral hernia, with inguinal canal/ring anatomy shown alongside an axial pelvic CT with an arrow to a bowel loop near the inguinal/femoral canal.
- The transition point is the CT sign to find: dilated loops on either side with arrows converging centrally on the transition point/mesenteric structure.
Warning
The hernia list on the slide is substantially covered by an overlapping CT image, so only the three types above could be confirmed from the slide.
Case 8: splenic rupture
Presentation: 25-year-old rugby player kicked in the abdomen in a ruck, now severe “terrible” abdominal pain, cannot move, generalised guarding. Temp 37, BP 80/50, HR 130.
Key points:
- Blunt abdominal trauma with hypotension and tachycardia indicates splenic rupture.
- Anatomy: the spleen sits with liver, stomach and pancreas; healthy and ruptured spleens are compared in situ. The splenic vasculature comprises the splenic artery and vein, short gastric arteries and the left gastro-epiploic artery, running with the pancreas.
- CT: axial upper abdominal CT shows altered splenic parenchyma with perisplenic fluid, consistent with laceration/haematoma.
- Angiographic signs: extracapsular active bleeding (contrast extravasation from the vessel) and a delayed phase blush around the spleen.
- Treatment by embolisation: femoral arterial access (common femoral artery, access sheath, at the level of the femoral head), then a splenic artery angiogram with the catheter tip advanced to the bleeding vessel, and deployment of embolisation coils.
- The aortic branch anatomy is reviewed because the splenic artery arises from the coeliac trunk, the route taken to reach the spleen.
- The case also covers the pathology of splenic rupture and post-splenectomy prophylaxis.
Important
Post-splenectomy prophylaxis shown on the slides: amoxicillin 500 mg capsules, meningococcal groups A, C, Y and W-135 conjugate vaccine (MCV4), meningococcal group B vaccine (Bexsero) and Haemophilus influenzae type b conjugate vaccine (Hiberix).
Case 9: appendicitis
Presentation: 14-year-old boy with tummy pain that came on when he got up in the morning, worsening through the school day, now constant and “gripping”; asked where the pain is he says all over but points to the umbilicus.
Pathophysiology, stage 1 as given: initiation of acute appendicitis with lumen obstruction and mucus accumulation. Potential causes of obstruction:
- Appendicoliths (faeces)
- Calculi
- Lymphoid hyperplasia
- Infection
- Benign or malignant tumours
Anatomy: caecum, ileum, mesoappendix and appendix, with the site of obstruction and accumulating mucus marked; a normal appendix is shown as an inset on the intestinal illustration.
Imaging:
- Coronal CT of the abdomen and pelvis.
- Axial CT with the appendix labelled.
- Ultrasound comparison of a normal appendix against an acutely inflamed one (“acute appy”), framed as normal versus abnormal.
Warning
Only stage 1 of the appendicitis sequence is recoverable: the right-hand side of the slide carrying the later stages is fully covered by an opaque block, and the bottom-right CT images on the following slide are cropped by the slide edge.
Case 10
Presentation: obese 25-year-old woman with intermittent severe abdominal pain, cramping and intense, lasting about a minute at a time; no periods for about 7 months; thinks she might have put on a bit of weight recently but has not felt like exercising much.
Imaging shown is a full AXR of the abdomen and pelvis showing the bowel gas pattern and pelvic bones, with no labels or arrows.
Warning
The case sub-heading on the following slide is covered by the overlapping X-ray image, so the diagnosis for case 10 is not confirmable from the slides.
Self-test
- List the pros and cons of CT for abdominal imaging as given in the lecture.
- List the pros and cons of ultrasound for abdominal imaging.
- List the pros and cons of MRI for abdominal imaging.
- List the pros and cons of plain abdominal X-ray.
- Describe the T stages of colorectal cancer by depth of invasion through the bowel wall.
- Which imaging modality is used for local T staging of a rectosigmoid tumour, and which for distant staging?
- A 30-year-old woman has severe right lumbar colicky pain in 10 minute spasms, cannot lie still, and has blood on urine dipstick. What is the diagnosis, and what imaging finding would you expect?
- Distinguish case 1 from case 3 given both are young women with overnight onset of worsening lateralised abdominal pain.
- Describe the stages and risk factors in the pathophysiology of abdominal aortic aneurysm.
- Explain the cycle of molecular mechanisms driving aneurysm formation and rupture.
- Name the fascial planes and retroperitoneal spaces identified on axial CT, and explain why they matter in a ruptured AAA.
- Compare AXR, CT, ultrasound and MRI for detecting gallstones and for detecting cholecystitis.
- List the ultrasound findings of acute cholecystitis with gallstones.
- On an AXR showing a calcified opacity in the right upper quadrant, what is the other calcified structure the lecture warns you to distinguish it from?
- Distinguish painful gallstone disease from the differential of painless jaundice in an older patient.
- A 42-year-old woman has colicky central pain, vomiting, absent bowel sounds and a previous appendicectomy. What is the diagnosis and what CT sign confirms it?
- List the hernia types given as causes of bowel obstruction.
- Describe the steps of angiographic embolisation for a bleeding spleen, from access to treatment.
- Which two angiographic appearances of splenic bleeding are illustrated?
- What antibiotic and vaccinations are shown for a patient after splenectomy?
- Describe stage 1 of acute appendicitis and list the potential causes of luminal obstruction.
- What ultrasound comparison is used to demonstrate appendicitis?
- Predict what would happen to modality choice if a patient with suspected gallstones were also very obese, and explain why.
- A 25-year-old rugby player is kicked in the abdomen and has BP 80/50, HR 130 and generalised guarding. What is the diagnosis, and which vessel would the interventional radiologist target?
- Using the case series, explain how the history alone shifts the imaging choice between renal colic, gastroenteritis and ruptured AAA.
Answers
Reveal answers
- Pros: fast, great resolution, available. Cons: radiation, thin patients.
- Pros: real time imaging, no radiation, accessible. Cons: operator dependant, not good with obese patients.
- Pros: excellent detail, identification of small lesions, characterisation. Cons: expensive, slow, sensitive to movement.
- Pros: cheap, fast, accessible. Cons: radiation, inaccurate, rarely changes management.
- T1 invades the submucosa; T2 invades the muscularis propria; T3ab and T3cd extend through the muscularis propria into and through the serosa, subdivided by depth; T4 invades an adjacent organ or structure.
- MRI of the pelvis in multiple planes and sequences for local T staging; PET or PET-CT with CT for distant/nodal and bone metastatic staging.
- Renal colic. Expect a dilated collecting system (hydronephrosis) on the affected side compared with the normal side, from obstruction by a renal stone.
- Case 1 has a urine dipstick positive for blood and right lumbar colicky spasms with inability to lie still (renal colic); case 3 has a dipstick negative for blood and a dragging right lower quadrant pain (ruptured ovarian cyst), diagnosed on pelvic ultrasound showing free fluid and an adnexal cyst.
- Initiation (genetics, gender, ethnicity, age), then progression (smoking, infection, trauma, hypertension), then rupture.
- Cytokines and inflammation drive oxidative stress and reactive oxygen species, which activate proteases and MMPs, causing vascular smooth muscle cell apoptosis and extracellular matrix degradation, which increase inflammation and re-enter the cycle.
- Planes: posterior peritoneum, anterior renal fascia, posterior renal fascia, lateroconal fascia, transversalis fascia. Spaces: anterior pararenal, perirenal, posterior pararenal. They define the retroperitoneal compartments into which aneurysmal haemorrhage tracks, seen as hyperattenuating material around the aorta and kidneys.
- AXR: good if calcified, otherwise useless, and cannot assess cholecystitis. CT: good if calcified, otherwise difficult, not great at cholecystitis. Ultrasound: great for all gallstones and for cholecystitis, cheap and quick. MRI: great for all gallstones and for cholecystitis, but not cheap and not quick.
- Thick gallbladder wall, free fluid, stones, and absence of echoes posterior to the calculi (posterior acoustic shadowing).
- A calcified mesenteric lymph node.
- Gallstone disease presents with jaundice combined with back/flank pain; the differential is painless obstructive jaundice caused by a tumour obstructing the biliary tree at the head of the pancreas/distal bile duct.
- Small bowel obstruction. The transition point on CT, with dilated bowel loops on either side and the change in calibre at a central mesenteric point; a normal CT is used for calibre comparison.
- Indirect inguinal, direct inguinal and femoral hernia (a strangulated hernia is shown causing obstruction). The slide list is partly obscured, so these are the confirmable types.
- Femoral arterial access at the common femoral artery with an access sheath at the level of the femoral head, catheter advanced via the aorta and coeliac trunk into the splenic artery, splenic angiogram to identify the bleeding branch with the catheter tip at the site, then deployment of embolisation coils.
- Extracapsular active bleeding (contrast extravasating from the vessel) and a delayed phase blush around the spleen.
- Amoxicillin 500 mg capsules, meningococcal A/C/Y/W-135 conjugate vaccine (MCV4), meningococcal group B vaccine (Bexsero) and Hib conjugate vaccine (Hiberix).
- Stage 1 is initiation with obstruction of the appendiceal lumen and accumulation of mucus. Causes of obstruction: appendicoliths (faeces), calculi, lymphoid hyperplasia, infection, and benign or malignant tumours. Later stages could not be transcribed as the slide is obscured.
- Side by side ultrasound of a normal appendix versus an acutely inflamed appendix (“acute appy”), framed as normal versus abnormal, alongside axial CT with the appendix labelled.
- Ultrasound is the first choice for gallstones and cholecystitis, but it is operator dependant and not good with obese patients, so image quality would suffer; MRI is great for all gallstones and for cholecystitis and would be the alternative, at the cost of expense and speed. CT is good only if the stones are calcified and is not great at cholecystitis.
- Splenic rupture. The splenic artery, reached from the coeliac trunk off the abdominal aorta, embolised with coils at the bleeding branch.
- Colicky loin pain with haematuria and inability to lie still directs to renal colic and CT of the urinary tract; a shared illness among flat-mates with vomiting and loose stools directs to gastroenteritis, where CT is essentially unremarkable; sudden searing pain radiating to the back in an older man with BP 70 systolic and a weak pulse of 120 directs to ruptured AAA and urgent CT of the aorta and retroperitoneum.