Differential Diagnosis for RUQ Mass And Pallor in A 9-Month-Old Infant

Serious illnesses may cause a decrease in growth and even weight loss, but normal growth should not eliminate serious diagnoses from your differential.

Hepatic neoplasm1. Although rare in children this age, an hepatic neoplasm (whether malignant, such as hepatoblastoma, or benign) can cause an asymptomatic abdominal tumor and must be considered in a young infant with an asymptomatic RUQ abdominal mass.
2. Jaundice may be a feature, but the lack of jaundice does not rule out this diagnosis.
Hydronephrosis1. An obstruction at the uretero-pelvic junction can lead to hydronephrosis and a palpable kidney, sometimes manifesting as a flank mass.
2. In the newborn, a multicystic kidney may cause such an obstruction.While possibly asymptomatic, hydronephrosis causing a 6 cm palpable mass would usually present with a urinary tract infection.
Neuroblastoma1. The most frequently diagnosed neoplasm in infants; more than half of patients present before age 2.
2. The tumor may present as a painless mass in the neck, chest, or abdomen.
3. Children with an abdominal neuroblastoma may be asymptomatic; however, they may also appear chronically ill and may have bone pain from metastases to the bone marrow or skeleton.
4. Fever, pallor, and weight loss are frequently presenting symptoms.
5. Neuroblastoma is a likely diagnosis in an infant younger than a year of age who has an asymptomatic RUQ abdominal mass and pallor and no jaundice.
Teratoma 1. This is a rare malignant tumor.
2. A teratoma may present as a painless abdominal mass without other symptoms or it may cause pressure effects on neighboring structures resulting in abdominal or back pain, nausea, vomiting, constipation, and/or urinary tract symptoms.
3. A rare form of cancer (which in itself is rare in children), teratoma should be considered, even if it is quite low on the list.
Wilms’ tumor(nephroblastoma)1. This is a likely diagnosis in a child with an asymptomatic RUQ abdominal mass who has no lymphadenopathy or jaundice on exam and who is growing and developing normally.
2. These tumors are often discovered by the parents or on routine examination.
3. The masses are generally smooth and rarely cross the midline.Associated symptoms occur in 50% of patients and include abdominal pain and/or vomiting; patients may also be hypertensive.
4. The median age at diagnosis is 3 years.

Consideration of the five more likely diagnoses for Asia:

  • Hepatic neoplasm (F) is consistent with her presentation and should be included in the differential. (More details about this condition are on the pages that follow.)
  • Asia’s age and the finding of pallor argue against hydronephrosis (G); however, it should be on the differential diagnosis, albeit lower than other causes.
  • Asia’s appropriate growth and lack of lymphadenopathy do not rule out neuroblastoma (H).
  • A teratoma (I) should be considered, although it is unlikely and Asia’s pallor and lack of symptoms argue against this diagnosis.
  • While Wilms’ tumor (J) should remain on the differential diagnosis, Asia’s age and the finding of pallor are two factors that argue against this diagnosis.
  • The following diagnoses are much less likely and would not be included in your initial differential diagnosis:
  • While an appendiceal abscess (A) may have fewer symptoms than acute appendicitis, a patient would typically have abdominal pain, fever, nausea, or anorexia.
  • Congestive heart failure (B) can lead to palpable hepatomegaly from right-sided heart failure; however, children with CHF have poor growth and very poor exercise tolerance.
  • Constipation (C) is the most common cause of a left-sided abdominal mass (especially in the LLQ from palpable stool in the sigmoid colon), usually mobile on palpation. It would not be palpable as an immobile RUQ mass. Also, typically there are other signs, such as a history of hard and/or infrequent stools.
  • Fatty liver disease (D), an increasing problem due to childhood obesity, could cause some palpable hepatomegaly, but this would just be a palpable liver “edge,” however, and not a full abdominal mass.
  • A hepatic abscess (E) can cause an abdominal mass. However, the child would typically have symptoms of hepatic dysfunction. An abscess can cause fevers, abdominal pain, malaise, and anorexia.