Abdominal POCUS

9.1 Core parameters

Abdominal aorta

  • Less than 3.0 cm: normal.

  • 3.0 cm or greater: AAA.

  • 5.0 cm or greater: high rupture risk; urgent vascular evaluation.

  • Symptomatic: urgent CT plus vascular/surgical evaluation.

Kidney length

  • 9–12 cm: typical adult.

  • Less than 9 cm: small.

  • Greater than 12 cm: enlarged.

Hydronephrosis

  • 0: none.

  • 1: pelvis only.

  • 2: pelvis plus some calyces.

  • 3: marked pelvis plus calyces.

  • 4: plus cortical thinning or chronic change.

Spleen length

  • 12 cm or less: normal.

  • Greater than 12 cm: splenomegaly.

  • 15 cm or greater: marked.

Bladder volume

  • Volume approximately 0.7 × length × width × height.

  • Greater than 300–400 mL suggests retention, institution-specific.

Free fluid eFAST

  • 0: none.

  • 1: trace or focal.

  • 2: moderate.

  • 3: large or generalized.

  • Positive if fluid is present in any location.

CBD diameter

  • Greater than 6 mm may suggest obstruction.

  • Normal upper limit increases with age and after cholecystectomy.

Gallbladder wall

  • 3 mm or less: normal.

  • Greater than 3 mm: abnormal; nonspecific.

9.2 eFAST

Views: RUQ/Morison, LUQ/splenorenal, pelvis, suprasplenic. Positive equals free fluid in any location. eFAST is a screening tool. Negative eFAST does not exclude all intra-abdominal injury.

9.3 Dengue — gallbladder wall thickness, optional disease-specific

  • GBWT less than 3 mm: lower immediate concern; standard monitoring.

  • GBWT 3 mm or greater: abnormal alert threshold; correlate WHO warning signs, haematocrit, platelets, AST; repeat in 4–6 hours if changing.

  • GBWT 5 mm or greater: higher-risk finding; improved specificity for severe dengue; reassess plasma leakage and organ impairment; more frequent monitoring, earlier intervention.

  • Serial increase: evolving plasma leakage; escalate.

  • Resolution: improvement; supports clinical recovery.

Meta-analysis: GBWT associated with severe dengue, odds ratio 2.35, 95% CI 1.88–2.82; pooled sensitivity approximately 88%, specificity approximately 63%. Supportive, not diagnostic. Nonspecific. Fast 4–6 hours. Measure inner mucosa to outer serosa. Document pericholecystic fluid, stones, ascites, and pleural effusions.

9.4 Abdominal decision-making

  • Aorta 3.0 cm or greater: confirm; asymptomatic → vascular referral plus CT; symptomatic/unstable → urgent vascular/surgical.

  • Hydronephrosis plus renal failure: urgent urology/nephrology; fever/sepsis → obstructed infected system → urgent decompression.

  • Free fluid plus trauma plus instability: may support operative intervention; stable → CT.

  • Free fluid plus nontrauma: ascites, peritonitis, malignancy, pancreatitis, post-procedural.

  • Small kidney: chronic disease, atrophy, congenital.

  • Enlarged kidney: obstruction, oedema, infection, infiltrative.

  • Splenomegaly: haematologic, infectious, malignant, portal hypertension.

9.5 Obstetric and gynaecologic focused POCUS

POCUS in obstetrics and gynaecology is a rapid, limited, clinician-performed bedside assessment intended to answer a specific clinical question or guide immediate management. It is an extension of the physical examination, not a substitute for comprehensive diagnostic ultrasound.

Scope

Focused questions include:

  • Is there an intrauterine pregnancy?

  • Is the pregnancy viable?

  • Where is the placenta relative to the internal os?

  • Is there free intraperitoneal fluid?

  • Is there an adnexal mass or gross uterine pathology?

  • Is there suspected ectopic pregnancy?

Imaging approach

  • Transabdominal ultrasound: initial pelvic evaluation, free fluid, uterine size, gross adnexal pathology, placental location in mid and third trimester when transvaginal scanning is not feasible.

  • Transvaginal ultrasound: preferred when feasible for early IUP confirmation, fetal cardiac activity, cervical length, placental relationship to internal os, suspected posterior placenta praevia, and small uterine or cervical lesions.

First-trimester assessment

The two primary questions are:

  1. Is there an intrauterine pregnancy?

  2. Is the pregnancy viable?

Viability is confirmed by fetal cardiac activity. POCUS is strongly recommended in symptomatic patients who present emergently in the first trimester.

Diagnostic performance

  • Visualization of an intrauterine pregnancy reduces the likelihood of ectopic pregnancy.

  • Reported sensitivity: 97%, 95% CI 92–99.

  • Reported specificity: 71%, 95% CI 60–80.

  • Negative predictive value: 99.96%, 95% CI 99.6–100.

  • POCUS with IUP visualization at admission was associated with a mean reduction in length of stay of approximately 73.8 minutes, 95% CI 49.1–98.6.

Antepartum haemorrhage

In patients with antepartum haemorrhage at 24+0 weeks or greater, POCUS is conditionally recommended to improve detection of low-lying placenta, placenta praevia, and abruption. Timely placental localization may reduce intraoperative placental transection, inform surgical planning, guide mode of delivery, and identify patients requiring referral to higher-level facilities.

Transvaginal assessment is preferred when available and safe. In patients with suspected placenta praevia on transabdominal ultrasound:

  • Positive predictive value: 99%.

  • Negative predictive value: 98%.

  • False-negative rate: 2.3%.

Gynaecologic focused assessment

Clinical indications:

  • Acute pelvic pain.

  • Abnormal uterine bleeding.

  • Early pregnancy evaluation.

  • Suspected ectopic pregnancy.

  • Adnexal mass.

  • Uterine fibroids.

  • Free intraperitoneal fluid.

  • Suspected pelvic inflammatory disease or tubo-ovarian abscess.

  • Preoperative or emergency triage.

Reported POCUS accuracy compared with formal radiology ultrasound:

  • Early intrauterine pregnancy: sensitivity 100%, specificity 100%.

  • Ectopic pregnancy: sensitivity 90%, specificity 98%.

  • Uterine fibroids greater than 2 cm: sensitivity 84%, specificity 96%.

  • Adnexal masses greater than 3 cm: sensitivity 88%, specificity 95%.

  • Small intrauterine lesions less than 2 cm: sensitivity 40%, specificity 98%.

  • Mean time to diagnosis: POCUS 12 ± 5 minutes versus formal ultrasound 95 ± 30 minutes.

Limitations

  • Reduced sensitivity for small intrauterine lesions, particularly less than 2 cm.

  • Operator dependence.

  • Limited scope relative to comprehensive ultrasound.

  • Performance varies with body habitus, pathology complexity, equipment quality, and scanning experience.

  • Not a substitute for formal imaging when detailed characterization is required.

9.6 Abdominal-specific pitfalls

  • Oblique aortic cross-section: falsely enlarged diameter.

  • Confusing spine with aorta.

  • Missing calcified wall or mural thrombus.

  • Normal fullness of collecting system mimicking mild hydronephrosis.

  • Pregnancy, young patients, or distended bladder causing mild dilation.

  • Bowel gas obscuring pelvis or suprasplenic area.

  • Normal small perisplenic or perihepatic fluid misleading in nontrauma.

  • Ascites may appear moderate or large; it is not necessarily acute haemorrhage.

  • Negative eFAST does not exclude all intra-abdominal injury.

  • Confusing upper pole of left kidney with spleen or vice versa.

  • Kidney length alone does not establish aetiology.

  • GBWT is nonspecific: cholecystitis, liver disease, hypoalbuminaemia, CHF, sepsis, malaria, leptospirosis, renal failure, ascites, bowel oedema.

  • CBD greater than 6 mm may be normal post-cholecystectomy or with age.

  • Small postoperative free fluid may be physiologic; increasing volume or new pericardial fluid is more concerning.

9.7 Obstetric/gynaecologic-specific pitfalls

  • Using transabdominal scanning alone when transvaginal scanning is safer and more accurate for placental localization.

  • Over-calling small intrauterine pathology on POCUS.

  • Assuming POCUS replaces comprehensive obstetric ultrasound.

  • Ignoring operator dependence, body habitus, and equipment limitations.

  • Failing to escalate when free fluid, ectopic features, or placental abnormality are present.