(b)  Kidneys. — Nephritis  constitutes  the  most  common  and  important
complication.  Toxic  or  febrile  albuminuria  occurring  at  the  height  of  the
fever  is  usually  transient  and  without  greater  significance  than  the  same
condition  in  other  diseases,  as  pneumonia.  Much  more  important  is  the
albuminuria  which  comes  on  with  the  fading  of  the  rash  or  during  the
stage  of  desquamation.  The  anatomical  condition  in  the  quickly  fatal
cases  is  that  of  a  glomerulonephritis  of  varying  intensity.  Clinically  the
following  grades  may  be  recognized:

1.  MUd  Catarrhal  Nephritis. — The  urine  remains  normal  in  amount.
It  contains  a  moderate  amount  of  albumin  and  a  few  tube-casts.  Cylin-
droids  are  present.  There  is  no  blood.  (Edema  is  slight  and  is  confined
to  the  eyelids  and  the  pretibial  areas.  The  process  may  last  a  few  weeks
and  terminate  in  complete  recovery  or  it  may  be  the  starting  point  of  a
chronic  nephritis.  Sudden  intensification  of  the  symptoms  may  occur
with  anuria  and  fatal  uraemia,  oedema,  or  effusion  into  the  serous  sacs  or
the  larynx.
2.  Graver  cases  with  increased  albumin,  casts,  and  blood.  The  urine
is  diminished  and  there  is  slight  or  moderate  cedema  of  the  face  and  lower
extremities.  Effusion  into  the  serous  sacs  may  occur.  The  symptoms  are
not  urgent,  but  anaemia  is  pronounced  and  the  nephritis  tends  to  become
chronic.  Uraemia  may  suddenly  develop.  When  apparent  recovery  takes
place  renal  inadequacy  is  often  established,  and  the  albuminuria  of
adolescence  or  the  nephritis  following  an  acute  illness  or  exposure  to  cold
years  afterwards  may  be  traced  to  this  condition.  These  are  the  cases
that  under  well-directed  treatment  frequently  end  in  recovery.
