Measurements

Quick normal measurement references. Values are practical guide ranges and should be adjusted for age, sex, body habitus and local protocol.

Abdomen

Measurement	Normal / Cut-off	Note
Liver span	<= 15 cm	Adult right lobe craniocaudal span; correlate with body habitus.
Spleen length	<= 13 cm	Use longitudinal maximal length; borderline values need clinical correlation.
Splenic vein diameter	<= 7 mm	Interpret with portal vein size, collaterals and spleen size.
Kidney size	~3 x 6 x 12 cm	Adult approximate AP x transverse x length; compare both kidneys.
Common bile duct	<= 6 mm	+1 mm per decade after 60 years; can be up to about 10 mm post-cholecystectomy.
Portal vein diameter	<= 13 mm	Measured at quiet respiration; interpret with portal hypertension signs.
Main pancreatic duct	<= 2-3 mm	Larger values may be age-related but need correlation.
Renal cortical thickness	>= 7 mm	Reduced in chronic parenchymal disease.
Appendix diameter	<= 6 mm	Compressibility and inflammatory fat are important.
Gallbladder wall	<= 3 mm	Measure when adequately distended.
Abdominal aorta	< 3.0 cm	>= 3.0 cm is aneurysmal in adults.

Measurement	Normal / Cut-off	Note
Ovarian follicle	< 3 cm	Simple follicle/cyst <3 cm is usually physiologic in reproductive age.
Simple ovarian cyst	< 3 cm	Often reported as follicle/physiologic cyst if simple and premenopausal.
Endometrium premenopausal	Variable	Depends on menstrual phase; correlate with cycle day.
Endometrium postmenopausal	<= 4 mm	For bleeding assessment; threshold varies with HRT/tamoxifen.
Ovarian volume	< 10 mL	Premenopausal reference; PCOS criteria need context.
Cervical length	>= 25 mm	Usually assessed transvaginally in mid-trimester risk assessment.
MCA RI intrauterine	> 0.7	Use gestational-age context and full fetal Doppler protocol.
AFI	5-24 cm	Common practical range; use local obstetric protocol.

Measurement	Normal / Cut-off	Note
RI of most vessels	< 0.7	General practical cut-off; always interpret by vessel and organ.
Renal artery RI	< 0.7	Higher values may suggest parenchymal disease/obstruction depending on context.
Carotid ICA PSV	< 125 cm/s	Used for <50% stenosis category when plaque criteria fit.
ICA/CCA PSV ratio	< 2.0	Interpret with ICA PSV and plaque.
Renal artery PSV	< 180-200 cm/s	Higher velocities may suggest stenosis depending on ratio and waveform.
Aortic aneurysm threshold	< 3.0 cm	Measure outer-to-outer wall diameter.
Superficial venous reflux	< 0.5 sec	Reflux threshold commonly >0.5 sec.
Deep venous reflux	< 1.0 sec	Common threshold for femoral/popliteal deep veins.

Measurement	Normal / Cut-off	Note
Thyroid lobe AP diameter	< 2 cm	Use with total lobe dimensions and gland volume.
Thyroid lobe volume	~10-15 mL each	Varies by sex, iodine status and body size.
Isthmus thickness	< 5 mm	Use with diffuse thyroid enlargement signs.
Cervical lymph node short axis	Usually < 10 mm	Morphology is more important than size alone.
Submandibular gland length	~3-4 cm	Compare both sides and echotexture.

Measurement	Normal / Cut-off	Note
Achilles tendon AP thickness	<= 6 mm	Measure in short axis; compare with symptoms.
Plantar fascia thickness	<= 4 mm	>4 mm supports plantar fasciitis in context.
Median nerve CSA	< 10 mm2	At carpal tunnel inlet; lab thresholds vary.
Rotator cuff tendon	No tear / normal fibrillar pattern	Measure defects, retraction and muscle atrophy when abnormal.
Joint effusion	Absent/minimal	Use contralateral side and clinical context.

Measurement

Normal / Cut-off

Note

Pyloric muscle thickness

< 3 mm

>=3 mm supports hypertrophic pyloric stenosis with clinical context.

Pyloric channel length

< 15-17 mm

Borderline values need repeat/dynamic assessment.

Appendix diameter

<= 6 mm

Compressibility and secondary signs matter.

Renal pelvis AP diameter

Age/GA dependent

Use antenatal/postnatal hydronephrosis charts.

Hip alpha angle

>= 60 degrees

Graf classification; use age-appropriate technique.

Kidney length

Age based

Approximate practical pediatric renal length guide; compare with height/body size and both kidneys.

Age	Normal	Note
Newborn	4.0-5.0 cm	Term neonate practical range.
1 year	5.5-7.0 cm
5 years	7.0-8.5 cm
10 years	8.5-10.0 cm
Adolescent	9.5-12.0 cm	Approaches adult range.

Spleen length

Age based

Use maximal longitudinal splenic length; values are practical upper-limit ranges.

Liver span

Age based

Right lobe craniocaudal span varies with body size; use as a quick screen only.

Thymic thickness on chest US

Age based

Thymus is normally prominent in young children and involutes with age; morphology matters.