Chapter 24: Nephrotic Syndrome versus Nephritic Syndrome

INTRODUCTION

Glomerulonephropathies are disorders that primarily affect the structure and function of the renal glomerular apparatus. Frequently encountered in clinical practice, glomerulopathies are usually suspected from the history and the urinary findings of hematuria, red cell casts, or proteinuria. There are many different causes of glomerular disease that can be generally classified into nephrotic syndrome, nephritic syndrome, and non-nephrotic proteinuria. However, there may be considerable overlap in their clinical presentation with some diseases presenting with components of more than one syndrome.

NEPHROTIC SYNDROME

General Considerations

Nephrotic syndrome is defined as: more than 3.5 g of proteinuria/24 h, serum albumin less than 3 mg/dL, edema, hyperlipidemia, and lipiduria. Nephrotic syndrome may appear as a primary (idiopathic) renal disease or occur in association with any of a number of systemic conditions and hereditary diseases. The most common primary glomerular diseases include focal segmental glomerular sclerosis (FSGS), minimal change disease (MCD), membranous nephropathy, and membranoproliferative glomerulonephritis (MPGN). In the United States, the most common cause of nephrotic syndrome is diabetes mellitus. Approximately one-third of patients with diabetes mellitus will develop nephrotic syndrome, predictably leading to kidney failure. Other systemic diseases that may lead to the nephrotic syndrome include systemic lupus erythematosus (SLE), human deficiency virus (HIV) infection, hepatitis B, hepatitis C, amyloidosis, leukemia/lymphoma, or solid organ malignancy.

Pathogenesis

Nephrotic syndrome generally reflects noninflammatory damage to the glomerular capillary wall. The underlying glomerular disease results in proteinuria, which occurs from alterations in the glomerular filtration barrier. This increases glomerular permeability to plasma proteins. Albumin is the principal urinary protein lost, but other plasma proteins lost in the urine include hormone-carrying proteins such as vitamin D–binding protein, transferrin, and clotting inhibitors.

Prevention

At present, we do not have means to prevent primary nephrotic syndrome. Secondary nephrotic syndromes can often be improved and sometimes completely reversed by treating and controlling the underlying disease.

Clinical Findings

A. Symptoms and Signs

Nephrotic syndrome can present as asymptomatic proteinuria, but the most common symptom and sign at presentation is edema. Edema occurs initially in areas of high intravascular hydrostatic pressure, such as in the feet and ankles, as well as in areas in where tissue hydrostatic pressure is lowest, such as the periorbital and scrotal areas. If the edema becomes generalized and severe, it can present as anasarca.

B. Laboratory Findings

1. Urinalysis

Urine dipstick often demonstrates 3+ to 4+ protein, and a 24-hour urine collection will demonstrate greater than 3.5 g protein/day. Proteinuria can also be estimated from a single urine specimen by calculating the ratio ...