Pyelonephritis: This is the most likely diagnosis given the patient's symptoms of fever, chills, right-sided costovertebral angle pain, tachycardia, and dysuria. Pyelonephritis is an infection of the kidney, and these symptoms are classic presentations.

Urinary Tract Infection (UTI): While pyelonephritis is a type of UTI that affects the upper urinary tract, a lower UTI (cystitis) could also present with similar symptoms, albeit typically less severe.
Nephrolithiasis (Kidney Stones): Kidney stones can cause severe pain, often radiating to the costovertebral angle, and can be associated with infection, making this a plausible diagnosis.
Prostatitis: In men, prostatitis (inflammation of the prostate) can cause urinary symptoms, pain, and fever, making it a consideration in the differential diagnosis.

Sepsis: Any infection, including pyelonephritis or a complicated UTI, can lead to sepsis, a life-threatening condition that requires immediate recognition and treatment.
Perinephric Abscess: A collection of pus around the kidney, which can occur as a complication of pyelonephritis. It's crucial to identify and treat promptly to avoid severe consequences.
Emphysematous Pyelonephritis: A rare but serious infection of the kidney where gas is produced in the tissue, often seen in diabetic patients. It requires urgent medical attention.

Xanthogranulomatous Pyelonephritis: A rare form of chronic pyelonephritis characterized by the destruction of renal tissue and the presence of granulomatous tissue.
Malakoplakia: A rare inflammatory condition that can affect the urinary tract and is associated with chronic infection and an abnormal immune response.

Urinalysis: To check for the presence of blood, protein, and bacteria in the urine.
Urine Culture: To identify the causative organism and guide antibiotic therapy.
Imaging Studies: Such as ultrasound or CT scan to evaluate the kidneys and urinary tract for stones, abscesses, or other complications.
Blood Tests: Including complete blood count (CBC) and blood cultures to assess for signs of infection or sepsis.

Antibiotics: The choice of antibiotic should be guided by local resistance patterns and the severity of the infection. Common initial choices include fluoroquinolones (e.g., ciprofloxacin), cephalosporins (e.g., ceftriaxone), or a combination of ampicillin and gentamicin. The patient should be started on empiric antibiotic therapy as soon as possible after obtaining urine and blood cultures.

Hydration: Encourage the patient to drink plenty of fluids to help flush out bacteria from the urinary tract.
Pain Management: Use analgesics as needed to manage pain and discomfort.
Rest: Recommend rest to help the body recover from the infection.