|ECR 2019 / C-2983|
|Typical and atypical swellings in the female groin|
Findings and procedure details
We present a pictorial review of presenting complaints affecting the adult female groin. In addition to the most common hernias and inflammatory conditions such as lymphadenitis, we describe less commonly encountered conditions including atypical hernias, canal of Nuck hydrocoele and perineal venous collaterals.
We have applied the 'surgical sieve' for our approach to formulating a differential diagnosis:
Non-congenital hernias, congenital, neoplastic, traumatic, infection/inflammation and vascular.
A hernia can be defined as a "condition in which part of an organ is displaced and protrudes through the wall of the cavity containing it (often involving the intestine at a weak point in the abdominal wall)" according to the Oxford Dictionary. This protrusion may contain intra-abdominal fat, bowel or other structures which have variable appearances on imaging. Diagnosis is usually clinical however there may be difficulty distinguishing between groin hernias clinically. Radiologically, these can often be distinguished by their anatomical location.
In order of incidence:
An indirect inguinal hernia arises lateral to the inferior epigastric vessels.
A direct inguinal hernia arises medial to the inferior epigastric vessels.
A femoral hernia protrudes through the femoral ring into the femoral canal which is posterior and inferior the the inguinal ligament (Fig 2).
An obturator hernia protrudes through the obturator canal between the obturator and pectineus muscles (Fig 3).
(If an appendix is contained within a femoral hernia it is termed a De Garengeot hernia - Fig 2).
The Canal of Nuck is a rare developmental abnormality that results due a failure of closure of the processus vaginalis which can result in a hernia or hydrocoele. This is comparable to the patent processus vaginalis in males.
The processus vaginalis usually obliterates before birth but if not, the abnormal patent pouch accompanies the round ligament via the inguinal canal into the labus majum. On ultrasound, it is appears as a cystic mass superficial and medial to the pubis at the level of the superficial inguinal ring (Fig 4).
Palpable or enlarging lymph nodes are a common reason for referral for ultrasound. The history and examination along with the ultrasound morphology can help differentiate reactive lymphadenitis from malignant lymphadenopathy.
Normal lymph node morphology (for comparison):
Small, ovoid, homogenous thin cortex, well defined margins, fatty hilum with central vessels (Fig 5).
Features that favour malignancy:
Large, round, focal thickening of cortex, necrosis, ill defined or irregular margins, loss of fatty hilum, vessels at the periphery +/-central (Fig 6).
Metastastic deposits can also affect the groin and should be considered in the differential for a groin lump especially in patients with a known history of previous cancer (Fig 7).
Infection / Inflammation
Infective / inflammatory processes can involve any of the tissues in the groin including the joints (Fig 8).
It is important to remember infection may also arise from elsewhere in the abdomen e.g. the gynaecological organs. This can track to the groin and present as a groin abscess such as in severe cases of pelvic inflammatory disease (Fig 9).
Ingrown hairs in the skin can lead to pilonidal cysts (Fig 10) which may become infected. These typically occurs in the intergluteal region especially in obese or hirsute patients but the condition may also affect the groin.
The most common traumatic groin swelling is a haematoma which would vary in appearance dependent on age. Fracture of the pelvis or femora may also be considered in elderly patients especially if presenting with a fall (Fig 11).
In intravenous drug users for a groin swelling, the differential also includes an injection tract (Fig 12). Intravenous drug injection can also lead to pseudoaneurysm.
Vascular conditions causing lumps in the groin may arise from the arteries, veins or occasionally lymphatics. The main pathologies involving the arteries are aneurysm, pseudoaneurysms, AV fistula. The most clinically emergent of these, pseudoaneurysm, is usually iatrogenic or secondary to intravenous drug use or trauma. Pseudoaneurysms and arteriovenous fistulas can also fall under the iatrogenic category in the surgical sieve.
A true aneurysm of the femoral artery is less common and usually occurs in the elderly. This involves all three walls of the artery whereas a pseudoaneurysm only involves the outer layers of the tunica media and adventitia (Fig 13).
Venous prominence can result from venous dilatation such as a saphenous varix or collaterals from obstruction such as from May Thurner syndrome (Fig 14) - chronic compression of the left common iliac vein by the overlying right common iliac artery.