CT abdomen is an increasingly common investigation that is used to help make diagnoses of a broad range of pathologies. A CT abdomen in its simplest form is a CT from diaphragm to symphysis pubis performed 60 seconds after pump-injection of iodinated contrast into a peripheral vein. However, depending on the clinical question, a variety of different protocols can be used.

Documents

1. USG of Whole Abdomen/HBS/Upper Abdomen/Pelvis/KUB.

2. MRI Whole Abdomen/MRCP/HBS/ Upper Abdomen/KUB/CT Urogram/ MR Urogram/IVU.

3. Serum Creatinine Report.

4. ±Operation Note.

5. History.

Preparation

1. খালি পেটে আসবেন (কন্ট্রাস্ট সিটি স্ক্যান এর জন্য)।

2. ২ লিটার পানির বোতল সাথে নিয়ে আসবেন।

3. পুরাতন কাগজপত্র সাথে নিয়ে আসবেন।

4. সুতি কাপড় পড়ে আসবেন।

Indications

1. Abdominal pain.

2. Abdominal sepsis.

3. Bowel obstruction.

4. Postoperative complications.

5. Vascular compromise, e.g. aortic aneurysm.

6. Infections such as appendicitis, pyelonephritis or infected fluid collections, also known as abscesses.

7. Inflammatory bowel disease such as ulcerative colitis or crohn's disease, pancreatitis or liver cirrhosis.

8. Cancers of the liver, kidneys, pancreas, ovaries and bladder as well as lymphoma.

9. Kidney and bladder stones.

10. Abdominal aortic aneurysms (aaa), injuries to abdominal organs such as the spleen, liver, kidneys, or other internal organs in cases of trauma.

Important pathology

1. Bowel obstruction.

2. Bowel perforation.

3. Colon cancer.

4. Intra-abdominal trauma.

Benefits

1. Relatively quick and accessible.

2. Reproducible findings.

3. Complete assessment of the abdomen and pelvis.

Limitations

1. Uses ionising radiation

a) Risk of radiation-induced cancer.

b) Approximately 100 times the dose of a chest radiograph.

2. Requires iodinated IV contrast

a) Risk of renal impairment.

b) Risk of anaphylactic reaction.

Procedure

1. Check renal function.

2. Lie patient supine on CT table.

3. Scout image to plan study.

4. I.V contrast injected via pump-injector.

5. 60-second delay.

6. Scan from dome of diaphragms to symphysis pubis.

Variations on a theme

Differing the IV contrast injection and timing may be useful.

1. Dual-phase CT abdomen

a) Two scans- non-contrast and arterial.

b) Assessment of vascular supply and parenchyma.

2. 3-phase CT abdomen

a) 3-phase non-contrast, arterial and porto-venous.

b) Assessment of vascular supply and parenchyma.

Phases of enhancement

The purpose of contrast-enhanced CT (CECT) is to find pathology by enhancing the contrast between a lesion and the normal surrounding structures.
Sometimes a lesion will be hypo-vascular compared to the normal tissue and in some cases a lesion will be hyper-vascular to the surrounding tissue in a certain phase of enhancement.
So it is important to know in which phase a CT should be performed depending on the pathology that you are looking for.

Scroll through the images to see the enhancement in the different phases.

Non-enhanced CT (NECT)
Helpful in detecting calcifications, fat in tumors, fat-stranding as seen in inflammation like appendicitis, diverticulitis, omental infarction etc.

Early arterial phase - 15-20 sec p.i. or immediately after bolus-tracking. This is the phase when the contrast is still in the arteries and has not enhanced the organs and other soft tissues.

Late arterial phase - 35-40 sec p.i. or 15-20 sec after bolus-tracking. Sometimes also called "arterial phase" or "early venous portal phase", because some enhancement of the portal vein can be seen. All structures that get their blood supply from the arteries will show optimal enhancement.

Hepatic or late portal phase - 70-80 sec p.i. or 50-60 sec after bolus-tracking. Although hepatic phase is the most accurate term, most people use the term "late portal phase". In this phase the liver parenchyma enhances through blood supply by the portal vein and you should see already some enhancement of the hepatic veins.

Nephrogenic phase - 100 sec p.i. or 80 sec after bolus-tracking. This is when all of the renal parenchyma including the medulla enhances. Only in this phase you will be able to detect small renal cell carcinomas.

Delayed phase - 6-10 minutes p.i. or 6-10 minutes after bolus-tracking. Sometimes called "wash out phase" or "equilibrium phase". There is wash out of contrast in all abdominal structures except for fibrotic tissue, because fibrotic tissue has a poor late wash out and will become relatively dense compared to normal tissue. This is comparable to late enhancement of infarcted scar tissue in cardiac MRI.

Oral contrast

Oral contrast is given in cases of suspected bowel perforation.

We use positive contrast: 1500 ml water with 50 cc non-ionic water soluable contrast.

Rectal contrast

Rectal contrast is given in cases of suspected bowel perforation.

We use positive contrast: 1000 ml water with 30 cc non-ionic water soluable contrast.

Contraindication

1. Hypersensitivity to iodinated contrast agent.

2. Pregnancy.

3. Irregular rhythm.

4. Renal insufficiency (serum creatinine > 1.5 mg/ml). Kidney disease.

5. Hyperthyroidism.

6. Inability to hold breath for 10 sec.

7. History of allergy to other medication.

8. Metallic interference (e.g: pacemaker, defibrillator wires).

9. Excessive radiation exposure.

10. Radioactive iodine treatment for thyroid disease.

Procedure (Bangla):

প্রথমে রোগীকে অল্প অল্প করে পানি খেয়ে প্রস্বাবের চাপ করতে বলি।
প্রস্বাবের চাপ হলে Plain Scan নিই।
Plain Scan নেওয়ার পর রোগীকে প্রস্বাব করে আসতে বলি।
প্যাথলজি Upper Abdomen এ থাকলে, ২ লিটার পানিতে 50 ml Inj, Iopamiro মিশিয়ে অল্প অল্প করে ২ ঘন্টা ধরে ১.৫ লিটার পানি খাইতে বলি। রোগীর প্রস্বাবের চাপ হলে আধা লিটার Oral Contrast মেশানো পানি খাওয়াইয়ে আই.ভি স্ক্যান নিই এবং ৫ মিনিট Delay Scan নিই। রোগীর Oral Contrast রেকটামে পোঁছানো পর্যন্ত আনুমানিক ৪ ঘন্টার সময় একটা স্ক্যান নিই।
প্যাথলজি lower Abdomen এ থাকলে, ১.৫ লিটার পানিতে 50 ml Inj, Iopamiro মিশিয়ে অল্প অল্প করে ২ ঘন্টা ধরে ১ লিটার পানি খাইতে বলি। রোগীর প্রস্বাবের চাপ হলে ১/২ লিটার Oral Contrast খাওয়াই এবং 500 ml Normal Saline with 15 cc contrast infusion set এর মাধ্যমে রেকটামে প্রবেশ করাই। তারপর I.V Scan নিই এবং ৫ মিনিট Delay Scan নিই।
পরীক্ষা শেষে, রোগীকে স্বভাবিক খাবারের সাথে বেশি করে পানি খাইতে বলি।

7. পরীক্ষা চলাকালীন সময়ে রোগীর কোন প্রকার সমস্যা দেখা দিলে রেডিওলজিষ্টকে অবহতি করতে হবে । পরীক্ষা পরবর্তী কোন সমস্যা হলে নিকটস্থ হাসপাতালের ইমার্জেন্সিতে যোগাযোগ করবেন।

PLANNING

Picture: CT Scan Abdomen Axial Planning.

Picture: CT Scan of Abdomen Coronal Planning.

Picture: CT Scan Image Bowel Wall Thickening.

ANATOMY

Abdomen

CT SCAN OF ABDOMEN