A child is brought to the doctor by his parents. The parents state that the boy's urine has developed an odd "tea" color. Physical examination reveals a well-behaved child who is normotensive with no evidence of discomfort or edema. Laboratory tests indicate normal renal function and normal levels of C3. The parents deny that the boy has had any recent sore throat or skin infections. They do, however, recall a recent transient gastrointestinal infection. Which of the following renal biopsy findings would best establish the diagnosis?

一名60岁男性因为呼吸困难2天前来急诊就诊。患者主诉无诱因发作持续性前胸胸闷，有压力感，伴活动耐力下降。既往能够爬3层楼梯，现在平路上走20米就觉得呼吸困难和胸痛，需要停下来休息。患者不能平躺，近2个晚上都是在沙发上睡觉。患者还主诉咳嗽，否认咯痰咯血。否认发热、寒战或盗汗。患者既往病史包括慢性阻塞性肺病、高血压、高血脂。患者使用药物包括沙丁胺醇和硝苯地平缓释片，但患者平时不需要戴氧气。患者有30包年的吸烟史，每天喝白酒50克。无药物过敏，无手术史，无相关家族史。入院生命体征：T 37.0°，HR 120，BP145/93, RR 30, SaO2 84%。患者肥胖。无颈静脉怒张。双肺底呼吸音下降，但无明显哮鸣音和啰音，心律齐，无心脏杂音，无第三心音。腹部平软，无压痛，肠鸣音正常。双下肢脚踝1+水肿。以下哪项为最先需要的诊断措施？

一名60岁男性因为呼吸困难2天前来急诊就诊。