NOS2 and pyelonephritis: Herein we confirm and extend our previous study by demonstrating that despite urine acidification, metabolic acidosis induced by dietary ammonium chloride (NH4Cl‐A) exacerbates cystitis and pyelonephritis in innate immune competent (C3H‐HeN) mice characterized by: (1) markedly elevated UPEC burden and increased chemokine/cytokine and NOS2 mRNA expression, (2) accumulation of intravesicular debris noninvasively detected by Power Doppler Ultrasound (PDUS), and (3) collecting duct (CD) dysfunction that manifests as a urine concentration defect.