Final answer:
Proteinuria is the manifestation in the patient that indicates the need for restriction of dietary protein in the management of APSGN.
Step-by-step explanation:
The manifestation in the patient that will indicate the need for restriction of dietary protein in the management of acute poststreptococcal glomerulonephritis (APSGN) is proteinuria.
Proteinuria is the presence of excessive protein in the urine, which is a common symptom of glomerulonephritis. Restricting dietary protein can help reduce the workload on the kidneys and prevent further damage.
Other manifestations of APSGN, such as hematuria, hypertension, and elevated blood urea nitrogen (BUN), may also be present but they do not specifically indicate the need for restriction of dietary protein.