The knotty problem in an infant girl's groin
Jul 1, 2005
By: Doran L. Fink, MD, PhD, Janet R. Serwint, MD
Mid-afternoon, and you're working at the pediatric clinic of your university hospital. With the beautiful spring weather outside, you've seen few acute care visits today; itchy eyes and runny noses in otherwise healthy children have established an unusually relaxing pace! Only one patient remains to be seen: a nearly 3-month-old girl whose mother is concerned about a "knot in the baby's groin."
Mom greets you with an uneasy smile as you enter the examination room. "It hasn't gone away," she says. "I think it's gotten bigger."
Instantly, you remember that the last time you saw the infant was four weeks ago—at her 2-month-old health maintenance visit. She had a diaper rash.
Reviewing your notes from that encounter, you recall that the rash had appeared one week before that visit. Apart from that, your patient was growing well, without complaints of fever, cough, congestion, diarrhea, or emesis. She was afebrile; vital signs were normal for age. You noted a pink, macular, anterior inguinal rash with satellite lesions that suggested diaper candidiasis. You also noted a firm, nontender, 1 x 1-cm mass in the right inguinal area that was freely mobile. Otherwise, the exam was unremarkable with no other rash or palpable mass.
Having decided that the inguinal rash was most consistent with a candidal infection and the mass most consistent with a reactive lymph node, you prescribed nystatin cream to be applied until three days after the rash resolved. You instructed the mother to return to the clinic if either the rash or the lymph node persisted for longer than several weeks. Now, four weeks later, she informs you that the rash did indeed improve within a week after the nystatin was started. The mass in the right groin has not disappeared as expected, however; instead, she reports that its size has nearly doubled!
The patient takes her lumps On further questioning, you learn that the mass has been present continuously over the past four weeks. It has remained nontender and does not appear to bother the baby when it is touched or when it is manipulated during a diaper change. The patient has regular, soft, yellow-to-brown bowel movements several times a day; no blood is obvious in the stool. She has had no emesis and has been taking formula well—four ounces every four or five hours. She has still not had a fever.
Today, rectal temperature is 36.4° C; heart rate, 150/min; and respirations, 42/min. Weight is 3.91 kg (between 5th and 10th percentiles for postconceptual age, tracking along her expected growth velocity). Overall, she is alert and active and appears well. The anterior fontanelle is soft; sclerae are clear; and a pupillary red reflex is present bilaterally. Tympanic membranes are unremarkable. Oropharynx is moist with no enanthem. Neck is supple without lymphadenopathy. Examination of the heart and lungs is unremarkable. The abdomen is soft and nontender, with normal bowel sounds and no organomegaly.
When you remove the girl's diaper, you discern the firm, freely mobile subcutaneous mass in the right inguinal region, midline along the path of the inguinal canal. The mass is 2 x 1.5 cm, nontender on palpation and manipulation, nonpulsatile, and lacking overlying skin changes. Turning to the left inguinal region, you palpate two firm, mobile, nontender masses, each 0.5 x 0.5 cm. You find no other palpable masses. Surveying the baby's skin carefully, you find no rashes anywhere. There are several small areas of hypopigmentation along the inguinal creases and inner thighs.
You're intrigued by the persistence of these inguinal masses. As a first step, the mother—20 years old, with negative serologic tests for syphilis, hepatitis B, and HIV infection—recounts her daughter's medical history for you.
The patient was born prematurely, at 35 weeks' gestation, product of an identical twin pregnancy. Vaginal delivery was complicated by breech presentation; the baby required positive pressure ventilation for several minutes for respiratory distress. Apgar score was 3 at one minute, 7 at five minutes, and 8 at 10 minutes. She was admitted to the neonatal intensive care unit, where she remained stable on room air. A workup for sepsis was negative. After two days in the NICU, she was transferred to the well-baby nursery. Three days later, she was discharged with her twin sister.
The patient had unremarkable health maintenance visits at 1 and 3 weeks of age. At 7 weeks, she was evaluated by your partner for an erythematous, maculopapular, scaling rash on the face and shoulders. Hydrocortisone 1% cream was prescribed for presumed seborrheic dermatitis, and the rash resolved after one week. She had no further medical concerns until that 2-month-old visit. At each visit, weight was at the 10th percentile for postconceptual age.
Differential diagnosis of inguinal mass in an infant
The patient takes no medications at the moment, has no known drug allergies or exposures to animals or insects, and has not traveled outside her home city. Her mother confirms a negative family history of inguinal hernia, malignancy, immunodeficiency, and lymphoproliferative disorders. The girl's twin sister has had no medical problems.
You suspect that the inguinal mass may be something other than a simple reactive lymph node that arose from candidal dermatitis. Although it has the feel of an enlarged lymph node, its persistence and gradual growth over the past four weeks—despite resolution of the rash—is somewhat unusual.
You consider possible causes of isolated inguinal lymphadenopathy:
reaction to infection of the inguinal area or lower extremities by various pathogens
bacterial infection of the lymph node itself
malignancy, including lymphoproliferative disorders
an immunodeficient state
an infiltrative process
You are reassured that many of these potentially serious conditions are quite rare in young infants and most often present with generalized, rather than localized, lymphadenopathy. You also wonder whether the mass is truly a lymph node. Its proximity to the inguinal canal suggests herniated bowel, omentum, or, even, an ovary. Femoral artery aneurysm is also a consideration, although an unlikely one because the mass is nonpulsatile. Last, you keep in mind other soft-tissue masses, such as fibroma and neuroma.
Pictures don't lie
Faced with a large differential diagnosis, you decide that imaging may narrow your focus or even identify the problem definitively. You discuss the case with the medical center's pediatric radiologist and together decide that ultrasonography (US) would most likely provide useful information, and would also have the benefits of quick performance and low risk.2 Good fortune! There's time in today's radiology schedule to perform the study.
The baby heads off to the radiology suite with her mother. Twenty minutes later, the radiologist calls you back. The sonogram revealed an indeterminate, well-defined hypervascular mass in the region of the inguinal canal. The right ovary could not be visualized, but the mass doesn't resemble normal or enlarged ovary, bowel, or adenopathic tissue. The radiologist recommends that you strongly consider herniated omentum—even though a lymph node or herniated ovary cannot be excluded.
As you wait for your patient to return, you contemplate what to do next. The sonogram suggests a hernia but she has no history of intestinal symptoms, no findings of acute abdomen on exam, and no tenderness in the mass. This may not be a surgical emergency, but you're uneasy about the persistence and gradual growth of the mass over almost a month's time.
You reason that, because US could not definitively identify the mass, evaluation by a surgeon may be warranted sooner rather than later. By the time she returns, you've arranged an appointment in the pediatric surgery clinic later that week.
Time to go inside Two days pass. You take a call from the surgeon, who is as perplexed as you are. He has decided to admit the girl that evening for exploratory surgery. His thinking is similar to yours: The preoperative differential diagnosis favors hernia with entrapped ovary versus lymphadenopathy. Preoperative lab tests, including a complete blood count, comprehensive metabolic profile, and coagulation panel, have already been performed, and all results are within normal limits.
Later that day, the surgeon pages you at home. Exploration of the right inguinal area revealed no hernia, and he removed a single large lymph node. Your patient tolerated the procedure well and was discharged home from the recovery unit. The excised node has been sent for histopathologic analysis.