The main concept is recognizing the umbrella term for stones that can occur anywhere along the urinary tract. Urolithiasis refers to stones in the urinary tract as a whole, derived from lith- meaning stone and -iasis indicating a condition. It’s the broad term used when discussing stones that can form in the kidney, ureter, or bladder. If a stone is located specifically in the kidney, the term nephrolithiasis is used. If it’s in the ureter, it’s ureterolithiasis. If it’s in the bladder, cystolithiasis. So urolithiasis is the general category, while the other terms pinpoint the exact location.

Burrows in the web spaces between the fingers and toes with intense itching is classic for scabies. The itching, often worst at night, comes from a hypersensitivity reaction to the mites, eggs, and feces that live in the superficial skin. The burrows themselves are thin, serpiginous tracks in the stratum corneum and are most evident in interdigital areas, wrists, and other flexural sites. This combination—severe nocturnal itching plus characteristic burrows in the web spaces—distinguishes scabies from other insect bites: bed bug bites tend to affect exposed skin and lack burrows; lice bites are associated with hair-bearing regions and nits; flea bites commonly cluster on the legs. Therefore, scabies is the most likely diagnosis. Treatment involves topical scabicides (like permethrin 5%) or oral ivermectin for the patient and close contacts, along with thorough cleaning of clothing, bedding, and environment.

typically develops bloody diarrhea. The Shiga toxin injures the vascular endothelium, especially in the kidneys, leading to microangiopathic hemolytic anemia, thrombocytopenia, and acute kidney injury. This makes bloody diarrhea caused by E. coli the best antecedent for HUS. The other events listed are not the usual triggers for classic HUS.

In cardiac arrest, reversible causes are grouped as H and T to guide rapid assessment and treatment during resuscitation. Hypoxia is the best answer because inadequate oxygen delivery to the heart and brain cripples electrical activity and pump function. Without sufficient oxygen, the myocardium cannot sustain contractions, so securing airway and ventilation to restore oxygenation is a foundation of resuscitation and can directly reverse the arrest. While myocardial infarction can trigger an arrest, it is not one of the H or T reversals themselves, and hyperthermia is not part of the standard H/T list (hypothermia is). Hyperglycemia isn’t a defined H/T reversible cause in this context either.