Background Overgrowth of calcium oxalate on Randall's plaque is a mechanism of stone formation among idiopathic calcium oxalate stone-formers (ICSFs). It is less clear how stones form when there is little or no plaque.Design, setting, participants, & measurements Participants were a consecutive cohort of ICSFs who underwent percutaneous nephroscopic papillary mapping in the kidney or kidneys containing symptomatic stones and a papillary tip biopsy from a representative calyx during a stone removal procedure between 2009 and 2013. The distribution of Randall's plaque coverage was analyzed and used to divide ICSFs into those with a high ($5%; mean, 10.5%; n=10) versus low (,5%; mean, 1.5%; n=32) amount of plaque coverage per papilla. Demographic and laboratory features were compared between these two groups.Results Low-plaque stone formers tended to be obese (50% versus 10%; P=0.03) and have a history of urinary tract infection (34% versus 0%; P=0.04). They were less likely to have multiple prior stone events (22% versus 80%; P=0.002) and had a lower mean 24-hour urine calcium excretion (187686 mg versus 291699 mg; P,0.01). Morphologically, stones from patients with low amounts of plaque lacked a calcium phosphate core by microcomputed tomography. Papillary biopsies from low plaque stone-formers revealed less interstitial and basement membrane punctate crystallization.Conclusions These findings suggest that other pathways independent of Randall's plaque may contribute to stone pathogenesis among a subgroup of ICSFs who harbor low amounts of plaque.

Rationale:Neuroblastoma is one of the most common tumors found in children, and mostly arises in the adrenal gland and paravertebral regions. Orbital neuroblastoma metastasis is relatively rare, and is associated with poor prognosis. Since the symptoms and signs of orbital neuroblastoma are not specific, its diagnosis remains challenging.Patient concerns:A 3-year-old girl presented with periorbital ecchymoses (raccoon eyes) and proptosis for 40 days.Diagnoses:Abdominal magnetic resonance imaging (MRI) and sonography analysis revealed a large mass in the left adrenal gland (primary tumor). The computed tomography and MRI further revealed multiple soft tissue masses in the skull and both orbits with erosion of the adjacent bones (the metastasis). The histological analysis of the tumor removed from the right orbit confirmed the diagnosis of neuroblastoma.Interventions:The mass on the right face was surgically removed.Outcomes:The patient exhibited no deteriorative signs at the 6-month follow-up.Lessons:Clinical manifestations, such as periorbital ecchymoses and proptosis, in combination with radiological analysis and histological findings, are important for the diagnosis of orbital neuroblastoma metastasis.