腎髓質鈣化症：十六病例的臨床分析

Medullary Nephrocalcinosis--Clinical Study of 16 Cases

腎髓質鈣化症(medullary nephrocalcinosis)是指腎實質的鈣質增加。在放射線學上可發現腎錐體處有成群的鈣化斑，這不單純表示腎的鈣化而已，更暗示有潛在的代謝功能障礙。本院七年來共經驗16個病例，平均年齡為38.3歲（14〜68歲），平均追蹤的期間為3.3年。在臨床表現方面：腰部酸疼者有10例(62.5%)；肌肉無力者5例(31.3%)，其中2例甚至發生急性呼吸衰竭而需使用呼吸器治療；腎性尿崩症而造成多尿症1例，泌尿道感染者1例；併有泌尿道結石者8例(50%)；1例因嚴重副甲狀腺機能過高症(primary hyperparathyroidism)而造成右腿骨疼痛，1例為選擇性1gA缺乏症所引起的慢性腹瀉。實驗室檢查方面：5例有高鈣血症(31.3%)，這些病患的潛在病因都為原發性副甲狀腺機能過高症，其中3位已接受副甲狀腺切除術。合併“遠端”性腎小管酸血症(“distal” renal tubular acidosis)有9例(56.3%)，其中5例為完全性腎小管酸血症者。而造成腎小管酸血症的相關病因中，3例為謝格連氏症候群 (Sjogren's syndrome)；3例有橋本氏甲狀腺炎(Hashiomoto's thyroiditis) ，其中2例分別合併謝格連氏症候群以及多器官自體免疫性疾病（包括：選擇性IgA缺乏症、原發性血小板缺乏性紫斑症及橋本氏甲狀腺炎）；1例為髓質海綿腎(medullary sponge kidney)合併不完全性腎小管酸血症；其餘3例，未發現有相關病因。在腎小管酸血症患者中，並未發現高尿鈣現象。在臨床上，完全腎小管酸血症病患皆表現出低血鉀週期性肌肉痲痺(hypokalemic periodic paralysis)；而經過檸檬酸鉀的治療，並無患者再發生；但有1例因泌尿道結石，須再接受體外震波碎石術(ESWL)。接受腎臟切片檢查有4例，其中3例呈現腎小管間質腎炎(tubulointerstitial nephritis)變化，這些病患均為腎小管酸血症患者；另一例呈現輕微球間質細胞增生，且無其它相關的明顯異常變化。慢性腎衰竭(chronic renal failure)是較需注意的長期併發症，但是腎鈣化本身很少直接造成腎衰竭，大部分是因為其他全身性疾病或潛在的其他腎臟病及併發症，如：泌尿道感染或高血壓等，而導致腎功能的變壞。本研究追蹤之16例病患中，13例腎功能都維持在正常範圍內，有3例(18.5%)為高血壓併慢性腎衰竭。其中1例因骨盆腔腫瘤出血而死亡。總之，本研究發現病人中最常見的潛在病因是原發性副甲狀腺機能過高症(31.3%)，謝格連氏症候群(18.7%)及橋本氏甲狀腺炎(18.7%)，而56.3%患者合併遠端性腎小管酸血症；在短期的臨床追蹤，大部份處於穩定狀態。

Medullary nephrocalcinosis (MN), is defined as an increase in the calcium content of the kidney that usually takes the form of small nodules of calcification clustered in each pyramid, and produces a similar (radiologic) picture whatever the cause. This radiologic finding carries much greater metabolic implications than does a single event of renal calculus. We collected 16 cases (14 wonen, 2 men) with radiological MN by sonography. Be mean age was 38.3 (14-68) years. Mean duration of follow-up was 3.3 years (8 months~6 years). The presenting symptoms and signs were flank pain (10), general weakness (5), polyuria (1), urinary tract infection (1), right thigh pain (1). Fifty percent of cases had evidence of urolithiasis. Five cases (31.3%) had hypercalcemia, and all of them resulted from primary hyperparathyroidism: three cases had a parathyroidectomy and one case died of pelvic tumor bleeding. Nine cases (56.3%) had evidence of distal renal tubular acidosis (dRTA): five cases were the complete type. Among of these, three cases resulted from Sjogren's syndrome (18.7%), and three cases had Hashimoto's disease (18.7%). One case of selective IgA deficiency was assotiated with thrombocytopenia and Hashimoto's thyroiditis, One case was medullary sponge kidney accompanied by incomplete dRTA. Distal RTA is either the cause of or secondary to MN. Patients with complete RTA had more symtomatic hypokalemia with general weakness (5/5), compared with the incomplete form (0/4). Unexpectedly, no evidence of hypercalciuria was detected among these cases. All RTA cases were treated with K- citrate for correcting metabolic acidosis, and hypokalemia and reducing the frequency of urolithiasis. During the follow-up period, none of our cases had recurrent symptomatic hypokalemia. The renal outcome was stable in most cases, except for three cases who also had hypertension. In conclusion, radiologic MN implicates a metabolic disorder of calcium. Once MN has become macroscopically visible, it usually persists for many years. Renal failure is the major long-term hazard faced by patients with MN. However, the problem is, to a large extent, a feature of the underlying renal disease and not simply a complication of nephrocalcinosis. The clinical condition of our patients was stable under short-term surveilence.