CT Abdomen and Pelvis — Portal Venous Phase

Diaphragm to the pubic symphysis (lesser trochanters where pelvic soft tissue matters).

Typical, not policy

Timings, volumes and delays here are representative values drawn from published guidance. Scanner generation, injector, cardiac output and local preference all move them. Confirm against your department's own protocol before you rely on a number.

When to use it

Undifferentiated acute abdominal pain in an adult where CT is the appropriate first cross-sectional test.
Suspected appendicitis, diverticulitis, bowel obstruction or perforation.
Suspected intra-abdominal collection or sepsis of unknown source.
Routine oncological staging, restaging and response assessment.
Post-operative complications where the question is collection, obstruction or ischaemia.

Technique

A delay of roughly 60-80 s from the start of injection gives peak hepatic and splenic parenchymal enhancement and good bowel wall enhancement — this is the default body phase.
Routine positive oral contrast is not required for most acute abdominal indications and delays the scan; it is a deliberate protocol choice, not a default.
Reformats in three planes are part of the standard, not an optional extra: coronal images materially improve detection of bowel wall and mesenteric abnormality.

Where it goes wrong

Using this single-phase protocol to characterise a liver or renal lesion under-calls hypervascular disease that is only visible arterially.
Scanning too early leaves the liver in a transitional phase with poor lesion-to-parenchyma contrast.
Giving positive oral contrast reflexively precludes converting the study into an angiographic or urographic protocol if the clinical picture changes.
A study cropped at the iliac crests misses pelvic pathology in a patient with "abdominal pain".

Clinical questions that reach this study

Suspected intra-abdominal abscess or collection Suspected appendicitis Suspected malrotation with midgut volvulus Major trauma — whole-body (pan-scan) versus selective CT Suspected acute diverticulitis Suspected bowel obstruction Suspected gastrointestinal perforation Suspected acute mesenteric ischaemia Acute pancreatitis — severity and complication assessment Suspected acute cholecystitis Obstructive jaundice and suspected biliary obstruction Suspected cholangiocarcinoma Colorectal cancer — staging Rectal cancer — local staging and restaging Crohn disease — small bowel assessment and monitoring Suspected perianal fistula or perianal sepsis Acute colitis Suspected deep vein thrombosis Acute pelvic pain in the reproductive age group (including suspected PID and tubo-ovarian abscess)Adnexal mass — characterisation and risk stratification Staging or completion CT in a known solid tumour Response assessment on systemic therapy Suspected or newly diagnosed lymphoma Metastatic disease with no identified primary

Contrast

Iodinated, intravenous

Typically 80-120 mL of non-ionic iodinated contrast at around 2.5-3.5 mL/s with a saline chaser; weight-based dosing is increasingly used.

NO ORAL CONTRAST, and that is a positive statement rather than an omission. The default assumption in a busy department is that an abdominal CT gets a drink; for acute abdominal pain, appendicitis and diverticulitis the evidence does not support it, intravenous contrast alone gives equivalent accuracy, and the 60-90 minute preparation is a real delay in a patient who may be septic or heading for theatre.
Positive oral contrast is a deliberate protocol choice for a specific question — suspected leak, fistula, or separating interloop abscess from bowel in a complex post-operative abdomen — not a default that gets switched off.
Giving it reflexively also forecloses options: dense luminal contrast prevents converting the study to an angiographic or urographic protocol if the clinical picture changes, and it can mask both mucosal hyperenhancement and an active bleeding point.

Acquisition

Breathing: Single breath-hold at end-inspiration.
Reconstruction: Thin axial reconstructions with coronal and sagittal reformats and a bone series.
Preparation: Fasting for a few hours is common practice where IV contrast is planned, though it is not a safety requirement for iodinated contrast. Oral contrast, if any, is a protocol decision and should not be given by default.

Phases

Each phase is authored once and shared across every protocol that uses it, so the physiology below is the same wherever you meet it.

Portal venous phaseTypically ~60–90 s after the start of injection. Confirm locally.
The portal vein and hepatic veins are opacified and the liver is at maximum parenchymal enhancement; bowel wall, mesentery, spleen and peritoneum are all well enhanced. The transferable principle is that HYPOVASCULAR lesions are most conspicuous when the BACKGROUND peaks, so this is the single most productive general-purpose abdominal phase and the correct default when the question is "what is wrong in this abdomen?". Its corollary is the classic error: a hypervascular lesion that was obvious 30 s earlier can become isodense and invisible here, so a normal portal venous study never excludes hypervascular disease.

Safety checks this protocol carries

Derived from the contrast agent and phases above, not authored here — which is why they cannot drift apart from what the protocol actually does.

Prior contrast reaction and elective premedication· nurse pre scan
Intravenous access adequate for the planned injection· radiographer at scan
Metformin and iodinated contrast· radiographer at scan
Child-sized technique and contrast dose· radiographer at scan
Pregnancy status before an ionising exposure· radiographer at scan
Kidney function and intravenous iodinated contrast· radiographer at scan