Inguinal regions — Reference values

Inguinal regions — Reference values: Minimum groin protocol, Mandatory anatomic landmarks, Indirect inguinal hernia, Direct inguinal hernia, Femoral hernia.

Category for targeted groin ultrasound: hernia, lymph node, mass, collection, vascular complication and postoperative assessment. There is no single universal system for all these findings; therefore the reading uses green for a complete dynamic exam without abnormality, yellow for small/indeterminate findings or divergent references, and red for complicated hernia, relevant femoral hernia, morphologically suspicious node, pseudoaneurysm, thrombosis or infection.

Measurements and reference values

Measurement	Usual value	Note
Minimum groin protocol	high-frequency linear + rest + dynamic maneuver	Use a high-frequency linear transducer and scan the painful point, inguinal canal, femoral region, femoral vessels and contralateral side when the finding is equivocal. Valsalva, coughing and upright scanning increase sensitivity for occult hernia.Source: ACR-AIUM-SPR-SRU abdomen parameter / RadioGraphics 2016 / HerniaSurge 2018
Mandatory anatomic landmarks	inferior epigastric vessels, inguinal ligament, femoral vein	Avoid abbreviations in teaching reports: write inferior epigastric vessels, inguinal canal, Hesselbach triangle, inguinal ligament, femoral vein and deep inguinal ring.Source: RadioGraphics 2016 / EPOS ECR 2023
Indirect inguinal hernia	lateral to the inferior epigastric vessels	The neck is usually at the deep inguinal ring and the contents may course through the inguinal canal toward the scrotum or labia majora.Source: RadioGraphics 2016 / AJR 2006
Direct inguinal hernia	medial to the inferior epigastric vessels	Occurs in Hesselbach triangle, above the inguinal ligament; posterior-wall bulging with Valsalva may precede an evident direct hernia.Source: RadioGraphics 2016 / EPOS ECR 2019
Femoral hernia	inferior to the inguinal ligament and medial to the femoral vein	It has a higher complication risk than inguinal hernia; bowel, pain, nonreducibility, sac fluid or obstruction signs should be communicated with priority.Small reducible fat: real finding, but management depends on symptomsBowel, pain or nonreducible: risk of incarceration/strangulationSource: HerniaSurge 2018 / Safer Care Victoria / EPOS ECR 2019
Hernia defect or neck	measure in millimeters	There is no universal normal cutoff: measure neck/defect, sac, contents, reducibility and behavior at rest/Valsalva/upright position. A small ultrasound-only hernia may not indicate surgery if minimal or asymptomatic.Source: HerniaSurge 2018 / Insights Imaging 2022 / Safer Care Victoria
Inguinal lymph node — short axis	<10 usual; up to 15 may be contextual mm	CT in asymptomatic patients found a mean of 5.4 mm and two standard deviations at 8.8 mm; Node-RADS accepts up to 15 mm for the inguinal region. On ultrasound, morphology matters more than size alone.Green: ≤8.8 mm, oval, fatty hilum, thin cortexYellow: 9-15 mm with preserved morphologyRed: >15 mm or suspicious morphologySource: Bontumasi AJR 2014 / Node-RADS / VITA-GLOWM
Inguinal lymph node — benign morphology	oval, central hilum, cortex <4 mm	Useful criteria: long-axis/short-axis ratio greater than 2, preserved fatty hilum, homogeneous cortex smaller than 4 mm and hilar or absent flow.Source: EPOS ECR 2023 inguinal nodes / superficial lymph node ultrasound reviews
Femoral pseudoaneurysm	arterial neck + bidirectional flow	The yin-yang color Doppler sign helps, but the more specific finding is to-and-fro flow in the neck communicating with the artery.Red: neck with to-and-fro flowSource: SRU vascular case / World Journal of Radiology
Canal of Nuck / female hydrocele	anechoic cyst in the female inguinal canal	May mimic hernia or lymph node. A cystic avascular lesion with posterior enhancement and no bowel continuity favors canal of Nuck hydrocele; look for peritoneal communication and complication.Source: J Ultrason 2024 / JSCR 2022

Classifications and calculators

Interactive assistant — inguinal region

Input	Output	How to use
Complete dynamic exam without finding	Green	Use only when rest, Valsalva/cough and, when needed, upright scanning were documented.
Small, fat-only or equivocal hernia	Yellow	Describe as real/possible finding, measure the neck and correlate symptoms; management may vary.
Femoral hernia, nonreducible bowel or compromise signs	Red	Communicate clinical priority: risk of incarceration, strangulation or obstruction.

Fill in the fields below to generate color reading, differentials and a next-step phrase.

Source: HerniaSurge 2018/2023 / RadioGraphics 2016 / ACR-AIUM-SPR-SRU

Anatomic map of groin hernia

Type	Ultrasound location	Points to report
Indirect inguinal	Lateral to the inferior epigastric vessels; enters through the deep inguinal ring and follows the canal.	Side, neck, content, reducibility, extension to scrotum/labia majora.
Direct inguinal	Medial to the inferior epigastric vessels, in Hesselbach triangle, above the inguinal ligament.	Posterior-wall bulge, neck, content and whether it appears only with strain.
Femoral	Inferior to the inguinal ligament, usually medial to the femoral vein.	Prioritize if pain, bowel, nonreducibility or sac fluid is present.
Recurrent / postoperative	Scan mesh margins and the inferomedial region with dynamic maneuver.	Differentiate recurrence from seroma, hematoma, fibrosis, plug/mesh and lymph node.

Source: RadioGraphics 2016 / EPOS ECR 2023 / AJR 2006

Inguinal lymph node — color reading

Color	Finding	Interpretation
Green	Short axis up to 8.8 mm, oval, long-axis/short-axis ratio >2, fatty hilum, homogeneous cortex <4 mm.	Compatible with reactive/benign node if clinical context matches.
Yellow	Short axis 9-15 mm with preserved hilum, diffuse cortical thickening or inflammatory context.	Common groin gray zone; size alone does not establish malignancy.
Red	Short axis >15 mm, round, absent hilum, eccentric cortex, necrosis/cystic change, interrupted capsule or peripheral/disorganized flow.	Suspicious, especially in skin, vulvar, penile, anal-canal cancer, melanoma, lymphoma or soft-tissue mass.

The inguinal region accepts larger nodes than other territories; therefore morphology and bilateral comparison are decisive.

Source: Bontumasi AJR 2014 / VITA consensus / EPOS ECR 2023

Practical differential diagnosis of a groin mass

Pattern	Possibilities	Alert
Increases with Valsalva or standing	Hernia, round-ligament varices, spermatic-cord varicocele, postoperative recurrence.	Confirm trajectory and relation to vessels/inguinal ligament.
Simple avascular cystic	Canal of Nuck hydrocele, spermatic-cord cyst, simple seroma.	Yellow if septated, painful, infected or with uncertain communication.
Solid oval with hilum	Reactive node, lower-limb dermatopathy, genital/perineal inflammation.	Do not use size alone; follow morphology.
Pulsatile vascular	Femoral pseudoaneurysm, arteriovenous fistula, thrombosed varix.	Spectral Doppler is mandatory before puncture.
Irregular or deep solid	Metastasis, lymphoma, sarcoma, inguinal-canal endometriosis, nerve-sheath tumor.	Consider additional imaging and local oncology pathway.

Source: JSCR 2022 / RadioGraphics 2016 / superficial lymph node ultrasound reviews

Report checklist — inguinal region

Item	Why it matters
Side and pain point	Avoids a generic report when the finding is focal or contralateral.
Rest, Valsalva/cough and upright position when needed	Without dynamic maneuver, an occult hernia may be missed.
Relation to inferior epigastric vessels and femoral vein	Classifies direct, indirect or femoral without difficult abbreviations.
Content and reducibility	Reducible fat, bowel, bladder/ovary, fluid and pain change priority.
Complication	Nonreducible content, thickened bowel, fluid, absent peristalsis, pseudoaneurysm, thrombosis or infection require explicit conclusion.

Source: ACR-AIUM-SPR-SRU / HerniaSurge / RadioGraphics

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