Fig.13.29 ).Inthecontextofpneumonias,theterm“consolidation,”usedfrequently,refersto“solidification”ofthelungduetoreplacementoftheairbyexudateinthealveoli.Patchyconsolidationofthelungisthedominantcharacteristicofbronchopneumonia,whileconsolidationofalargeportionofalobeorofanentirelobedefineslobar pneumonia (Fig.13.30 ).Theseanatomiccategorizationsmaybedifficulttoapplyinindividualcasesbecausepatternsoverlap,andpatchyinvolvementmayevolvetobecome
Fig. 13.29 Theanatomicdistributionofbronchopneumoniaandlobarpneumoniaaffectingthelowerlobesofthelung.
Fig. 13.30 Lobarpneumoniawithgrayhepatization.Thelowerlobeisuniformlyconsolidated.
confluentovertime,producingcompletelobarconsolidation.Moreover,thesameorganismsmayproduceeitherpatterndependingonpatientsusceptibility.Mostimportantfromtheclinicalstandpointareidentificationofthecausativeagentanddeterminationoftheextentofdisease.
Inlobar pneumonia,fourstagesoftheinflammatoryresponsehaveclassicallybeendescribed.Inthefirststageofcongestion, thelungisheavy,boggy,andred.Itischaracterizedbyvascularengorgement,intraalveolarfluidwithfewneutrophils,andoftenthepresenceofnumerousbacteria.Thestageofred hepatization thatfollowsischaracterizedbymassiveconfluentexudation,asneutrophils,redcells,andfibrinfillthealveolarspaces(
Fig.13.31A ).Ongrossexamination,thelobeisred,firm,andairless,withaliver-likeconsistency,hencethetermhepatization.Thestageofgray hepatization thatfollowsismarkedbyprogressivedisintegrationofredcellsandthepersistenceofafibrinosuppurativeexudate(see
Fig.13.31B ),resultinginacolorchangetograyish-brown.Inthefinalstageofresolution, theexudatewithinthealveolarspacesisbrokendownbyenzymaticdigestiontoproducegranular,semifluiddebristhatisresorbed,ingestedbymacrophages,expectorated,ororganizedbyfibroblastsgrowingintoit(
Fig.13.31C ).Pleuralfibrinousreactiontotheunderlyinginflammationisoftenpresentintheearlystagesiftheconsolidationextendstothesurface(pleuritis). Itmayresolveorundergoorganization,leavingfibrousthickeningorpermanentadhesions.
Fociofbronchopneumonia areconsolidatedareasofacutesuppurativeinflammation.Theconsolidationmaybeconfinedtoonelobebutismoreoftenmultilobarandfrequentlybilateralandbasalbecauseofthetendencyofsecretionstogravitatetothelowerlobes.Well-developedlesionsareslightlyelevated,dry,granular,gray-redtoyellow,andpoorlydelimitedattheirmargins.Histologically,aneutrophil-richexudatefillsthebronchi,bronchioles,andadjacentalveolarspaces(see
Fig.13.31A http://ebooksmedicine.net
Fig. 13.31 (A)Acutepneumonia.Thecongestedseptalcapillariesandexten-siveneutrophilexudationintoalveolicorrespondtoearlyredhepatization.Fibrinnetshavenotyetformed.(B)Earlyorganizationofintraalveolarexu-dates,seeninareastobestreamingthroughtheporesofKohn(arrow).
(C)Advancedorganizingpneumonia,featuringtransformationofexudatestofibromyxoidmassesrichlyinfiltratedbymacrophagesandfibroblasts.