Which of the following is the most common substance found on analysis of a renal stone?

A. Urinary tract infection
The symptoms described, including recent mental status changes and periods of incontinence, are suggestive of a urinary tract infection (UTI) in an elderly individual. UTIs are common among older adults and can cause a variety of symptoms, including confusion, which is often the primary manifestation in the elderly population. Other symptoms can include urinary urgency, frequency, and incontinence.

B. Acute kidney failure - While acute kidney failure can cause changes in urination and mental status, it is less likely to be the primary cause of these symptoms in this scenario. UTI is a more common and immediate concern given the symptoms described.

C. Septic shock - Septic shock is a severe condition that occurs when an infection leads to a life-threatening drop in blood pressure. While septic shock can cause altered mental status, it is a critical condition that often presents with more dramatic symptoms and requires immediate intensive care management. The symptoms described are more suggestive of a UTI.

D. Urinary stasis - Urinary stasis refers to the slowing or cessation of urine flow. While urinary stasis can contribute to the development of UTIs, it is not a condition that would cause sudden and acute mental status changes and incontinence on its own. UTI is a more likely cause of the symptoms described.

A. "UTI’s can be caused by urethrovesical reflux which is the backward flow of urine from the urethra to the bladder after coughing, sneezing, or straining":

This statement is correct. Urethrovesical reflux can contribute to UTIs, especially in women, as it can introduce bacteria from the urethra back into the bladder.
B. "UTI’s are more common in women due to their longer urethras":

This statement is correct. Women have shorter urethras than men, which makes it easier for bacteria to travel into the bladder, increasing the risk of UTIs.
C. "Glycosaminoglycan (GAG) is a protein in the urinary tract that exerts a nonadherent protective effect against various bacteria":

This statement is correct. Glycosaminoglycan is a substance that lines the urinary tract and helps prevent bacterial adherence, thereby protecting against UTIs.
D. "The organism most often responsible for UTI's in older adults is staphylococcus":

This statement is incorrect. The most common bacteria responsible for UTIs are Escherichia coli (E. coli), not staphylococcus.
E. "The normal urinary tract is sterile above the urethra":

This statement is correct. Normally, the urinary tract above the urethra is sterile, devoid of bacteria. UTIs occur when bacteria enter and multiply in the urinary system, leading to infection.