Final answer:
The symptoms of gross hematuria, suprapubic pain, and abrupt onset of illness less than three days suggest acute cystitis, a bacterial infection of the bladder.
Step-by-step explanation:
The symptoms described, including gross hematuria, suprapubic pain, abrupt onset of illness, and duration of symptoms less than three days, are most indicative of acute cystitis. Acute cystitis, which often results from a bacterial infection of the bladder, can present with gross hematuria (visible blood in the urine), dysuria (burning or pain during urination), and bladder pain. These symptoms align with the clinical manifestations of cystitis rather than acute pyelonephritis, which typically includes severe back pain, fever, and potential systemic symptoms, or chronic conditions like bacterial prostatitis and chronic pelvic pain syndrome (CPPS), which have a longer duration of symptoms.