Diagnostic Testing for a 9-Month-Old with Cough and Rib Fractures
This infant requires an immediate complete skeletal survey to evaluate for child physical abuse, as rib fractures in a 9-month-old are highly suspicious for inflicted injury regardless of the presence of cough. 1, 2
Primary Concern: Child Physical Abuse
Rib fractures in infancy are overwhelmingly caused by severe physical abuse. The presence of cough does not adequately explain rib fractures at this age—accidental rib fractures in infants are exceedingly rare and result only from massive trauma 3. While cough-induced rib fractures do occur, they are documented primarily in adults and older children with underlying conditions, not in healthy 9-month-old infants 4, 5.
Mandatory Imaging
Complete skeletal survey (21 images) must be performed immediately 1, 2:
- Frontal views of all appendicular skeleton
- Frontal and lateral views of axial skeleton
- Oblique chest views (critical for detecting rib fractures with higher sensitivity and specificity)
- Full 4-view skull series
Follow-up skeletal survey at 2-3 weeks is necessary when abuse is strongly suspected, as it identifies fractures missed initially and improves both sensitivity and specificity. Studies show 13 of 19 fractures were detected only on follow-up examination 1.
Bone scintigraphy should complement the skeletal survey—it has high sensitivity for detecting acute rib fractures that may be invisible on radiographs and revealed 8 previously undetected rib injuries in documented abuse cases 3.
Essential Laboratory Testing
The following labs are required for all young children with fractures concerning for abuse 1:
Metabolic bone disease screening:
- Serum calcium, phosphorus, alkaline phosphatase
- Parathyroid hormone and 25-hydroxyvitamin D
- Urinary calcium/creatinine ratio
Screening for occult trauma:
- Liver function tests, amylase, lipase (when multiple injuries identified)
- Urinalysis for occult blood
Consider if radiographic metaphyseal abnormalities present:
- Serum copper, ceruloplasmin, vitamin C (to exclude scurvy, copper deficiency, Menkes disease)
Physical Examination Priorities
Look specifically for:
- Bruising in non-cruising infants or unusual locations (ears, neck, trunk)—the most common injury from abuse
- Blue sclerae (osteogenesis imperfecta)
- Sparse, kinky hair (Menkes disease)
- Other occult injuries
Critical Pitfall
Do not attribute rib fractures to cough in a 9-month-old infant. The single case report of osteogenesis imperfecta presenting with "rickets-like rib fractures" and pneumonia 6 reinforces that when rib fractures occur with respiratory symptoms in infants, underlying bone disease or abuse must be investigated—not assumed to be cough-related. Cough-induced fractures occur in older patients, typically involving middle and lower ribs (especially 10th rib), and are not documented in healthy infants 5.
Child Protection Action
Given that 15 of 18 infants with rib fractures in one series had confirmed abuse 3, and that rib fractures may be the only finding in isolated abuse cases, immediate child protective services notification is mandatory while the diagnostic workup proceeds. The guidelines explicitly state skeletal survey is necessary for all children 0-23 months with rib fractures regardless of history 2.