A femoral hernia accounts for approximately 5-10% of all groin hernias in adults. Misdiagnosis in children, in whom the condition is rare, has been well recognised and documented. The aim of this study was to assess the accuracy of diagnosis in an adult population. Methods: An analysis of 379 patients with a groin hernia, presenting electively to a University Department of Surgery and entered into a prospective clinical trial. Results: A femoral hernia was confirmed at operation in 12 (3%) patients while a further 4 had a preoperative diagnosis of a femoral hernia. The correct diagnosis of a femoral hernia was made in only 3 cases by general practitioners and in only 6 by surgical staff of all grades. Conclusion: These data suggest that medical staff of all grades may be poor at diagnosing a femoral hernia and a change in the way we are taught to differentiate between femoral and inguinal hernia needs to be considered.
Keywords: Diagnosis, elective, femoral, hernia
J.R.Coll.Surg.Edinb., 46, February 2001, 117-18
The ability to differentiate a femoral from an inguinal hernia is important, as the cumulative probability of strangulation for a femoral hernia is around 20% at 3 months and 45% at 21 months. This compares with a probability of strangulation for an inguinal hernia of 3 and 4.5%, respectively, over the same time period.1 Though a femoral hernia accounts for less than 1% of all groin hernias in children, in adults it is more common accounting for approximately 5-10% of groin hernias. Previous studies have highlighted the problem of misdiagnosis in children but little work has been done to evaluate the problem in adult practice.2 This prompted us to look at our data to assess the rate of misdiagnosis in an adult population.
PATIENTS AND METHODS
The records of 379 patients taking part in a prospective clinical trial3 on the surgical management of groin hernia were examined to identify those who were determined preoperatively to have a femoral hernia and also those who were confirmed at operation to have a femoral hernia. Enrolment into the trial was between January 1994 and January 1997 and all data was recorded on a patient proforma and a computerised database. The patients were referred to the department by a number of local general practitioners and examined in the hospital outpatient clinic by one of five surgeons (two Senior House Officers, one Specialist Registrar and two Consultants). Patients admitted directly to the hospital and requiring emergency surgery were excluded from the study.
From our population of 379 patients a femoral hernia was identified at operation in 12 patients. Nine were female while three were male (median age 50, range 24-91). In one patient with sub-acute small bowel obstruction the diagnosis was made at laparoscopy (Table 1). The correct diagnosis of femoral hernia was made in only three of these patients by the general practitioner and in only six by hospital surgical staff. In addition, a diagnosis of femoral hernia was made by the hospital surgical staff in four female patients who at operation had an inguinal hernia. The general practitioner made the correct diagnosis in two of these patients. Diagnostic performance in terms of sensitivity, specificity and positive predictive value was 27%, 99.5% and 25%, respectively, for general practitioners compared with 50%, 99% and 37.5% for all grades of surgical staff.
Table 1: Preoperative diagnosis by general practitioner (GP) and hospital surgical staff
|Patient||Sex||GP||Surgeon (Grade)||Operative findings|
|8||F||Femoral (CP)||Femoral (SHO)||Femoral|
|13||F||Pain||Femoral (C)||Inguinal (Indirect)|
|14||F||Femoral||Femoral (SHO & C)||Inguinal (Indirect)|
|15||F||Inguinal||Femoral (C)||Inguinal (Indirect)|
|16||F||Inguinal||Femoral (SpR)||Inguinal (Direct)|
RSSBO: Recurrent subacute small bowel obstruction; SHO: Senior House Officer; SpR: Specialist Registrar; C: Consultant; CP:Consultant Physician
This study has shown that both general practitioners and surgeons of all grades are poor at differentiating femoral from inguinal hernias. A Medline search using the keywords femoral, hernia and diagnosis (with delimiters English language and human) revealed only two previous studies that have included both elective and emergency diagnosis of a femoral hernia.4,5 These show good agreement with the present study for general practitioners with only 30% of all femoral hernias being correctly diagnosed. Results for hospital staff, however, are significantly better with the correct diagnosis being made in 80%-90% of cases. However, these studies differ from the current study in a number of important ways. Over 60% of cases in both studies were urgent admissions, that is direct hospital admissions, while all patients in the current study were elective admissions through the outpatient clinic. The previous studies concentrated only on femoral hernias diagnosed at operation whereas we felt that a more accurate representation of the degree of error would be to include those patients who were diagnosed as having a femoral hernia preoperatively, but who subsequently turned out to have an inguinal hernia. Finally, all diagnoses in the current study were entered prospectively on a database as part of a large clinical trial where a Data Committee monitored data entry.
An important aspect of this study is its significance in relation to what medical students should be taught when trying to differentiate between femoral and inguinal hernias. Most textbooks describe the relationship of the hernia to the pubic tubercle as a critical landmark in this examination.6 An inguinal hernia is said to lie above and medial to the pubic tubercle whereas a femoral hernia lies lateral and below. This, however, is not strictly true as the internal ring is always lateral to the femoral canal and a small indirect inguinal hernia will therefore be lateral to the pubic tubercle. Also, a direct hernia will be lateral to or above the pubic tubercle. An alternative suggestion to help differentiate between femoral and inguinal hernias is the invagination test. However, this is only possible in men with indirect hernias and, as every student knows, most femoral hernias occur in females. We suggest that a better test might be to ask the student to place their finger over the femoral canal for reducible hernias and then ask the patient to cough. This landmark is easily felt either by following the adductor longus tendon to below the inguinal ligament and then placing ones fingers anterior and lateral to the tendon or alternatively palpating the femoral artery and placing ones hand approximately a finger breath medial to it.
When the patient coughs a femoral hernia should remain reduced while an inguinal hernia will re-appear as an obvious swelling.
The correct diagnosis of a femoral hernia is important as these patients should have an early outpatient appointment and receive rapid surgical treatment. The current study highlights our inability to make the diagnosis correctly and suggests a change in the way we examine these patients.
Copyright date: 15th June 2000
Correspondence: Professor PJ O’Dwyer, University Department of Surgery, Western Infirmary, Glasgow G11 6NT, U.K.
©2001 The Royal College of Surgeons of Edinburgh, J.R.Coll.Surg.Edinb.